An annealing process and apparatus

Abstract

This invention discloses an annealing process and apparatus, belonging to the field of metal heat treatment technology. The annealing process includes the following steps: a metal strip with a hardness of 68–79 after quenching is placed into an annealing furnace, subjected to alternating vacuum and inert gas replacement, heated and held at 370℃–390℃ for 10–14 hours, and then sequentially cooled to ≤45℃ using air cooling, inert gas pressurization, and water cooling, ultimately controlling the strip hardness within the range of 40±5. Annealing parameters can be adjusted according to the strip thickness. The annealing furnace apparatus includes a base, an inner cover, and an outer cover. The base provides a sealed connection to the pipelines, the inner cover forms a closed annealing space and is equipped with an annular pipe, and the outer cover provides heating and heat preservation. A baffle is provided on the inner side of the inner cover to assist in cleaning and protection. This invention solves the problems of unstable hardness control, poor device sealing, and easy oxidation and adhesion of the strip in traditional processes, improving production efficiency and product quality, and adapting to the needs of large-scale, high-precision production.

Description

Technical Field

[0001] This invention relates to the field of metal heat treatment technology, and in particular to an annealing process and apparatus. Background Technology

[0002] In the metal strip processing industry, the hardness of the material after quenching is typically in the range of 50–65 HRB. However, some downstream applications (such as deep drawing, precision bending, and cold forming) explicitly require the material hardness to be controlled at around 40 to facilitate subsequent processing, reduce mold wear, and improve yield.

[0003] Currently, the industry commonly uses multiple annealing furnaces in combination, typically requiring three or more furnaces operating in series or parallel. This method has the following drawbacks: 1) Unstable hardness control: Traditional annealing processes often exhibit hardness fluctuations exceeding ±10, making it difficult to consistently achieve the required 40±5. 2) High equipment investment: Multiple annealing furnaces and their associated systems significantly increase equipment costs, floor space requirements, and maintenance expenses. 3) Poor process consistency: Reliance on operator experience leads to significant quality fluctuations between different batches. 4) High energy consumption: Traditional processes often employ high-temperature, short-time annealing, resulting in high energy consumption and a tendency to cause surface oxidation.

[0004] Therefore, there is an urgent need in this field for a novel annealing method that can reliably achieve the target of low hardness, reduce the number of equipment, and improve process consistency. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of unstable hardness control, poor batch consistency, insufficient sealing performance of annealing furnace, low temperature control accuracy, easy oxidation and adhesion of strip and low production efficiency in the traditional annealing process. Therefore, an annealing process and device are proposed.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An annealing process and apparatus thereof, comprising the following steps: Step S1: Load the quenched metal strip with a hardness of 68–79 into the annealing furnace. Step S2: Perform vacuum-inert gas alternating replacement in the furnace to reduce the oxygen content in the furnace; Step S3: Heat and hold at a temperature range of 370℃–390℃ for 10–14 hours; Step S4: Cool the temperature to ≤45℃ in stages using air cooling, inert gas pressurization, and water cooling in sequence; Step S5: Finally, the hardness of the strip is controlled within the range of 40±5.

[0007] In some embodiments, when the thickness of the metal strip is 0.8 mm, the annealing temperature is 390°C, the holding time is 12–14 hours, and the hardness is reduced to 39–45.

[0008] In some embodiments, when the thickness of the metal strip is 0.9–1.0 mm, the annealing temperature is 380–385 °C, the holding time is 11–12 hours, and the hardness is reduced to 40–45.

[0009] In some embodiments, when the thickness of the metal strip is 1.5 mm, the annealing temperature is 380–390 °C, the holding time is 11–12 hours, and the hardness is reduced to 42–50.

[0010] The present invention also discloses an annealing furnace device suitable for annealing process, including a base, an inner cover and an outer cover. The base is used to provide a stable installation foundation and realize sealing and pipeline connection. The inner cover is used to form a closed annealing space. The outer cover is used to realize heating and heat preservation functions. The three are coordinated to adapt to each step of the annealing process.

[0011] In some embodiments, the base is horizontally fixed to the ground, and the top is provided with an annular sealing groove and a positioning protrusion. A high-temperature resistant sealing ring is embedded in the sealing groove to ensure the sealing performance inside the furnace. The positioning protrusion is used to position the material rack that carries the metal strip. The base integrates cooling water pipes and reserves a vacuum pump interface and an inert gas inlet / outlet interface to adapt to water cooling, vacuuming and gas replacement steps respectively.

[0012] In some embodiments, the inner cover is a sealed structure made of high-temperature and corrosion-resistant material. The bottom is sealed to the base, and the top is provided with a lifting device, a vacuum pump interface and an inert gas inlet / outlet interface. The inner side is provided with an annular pipe for airflow circulation and uniform gas distribution to ensure the uniformity of annealing atmosphere and temperature.

[0013] In some embodiments, the outer cover is fitted over the outer side of the inner cover and is made of heat-insulating and high-temperature resistant material. It has a heating element inside and is connected to an external temperature control system to precisely control the annealing temperature at 370°C–390°C. The outer cover has corresponding interfaces and lifting parts to accommodate cooling steps and hoisting operations.

[0014] In some embodiments, the annular tube is distributed along the height direction of the inner cover and communicates with the inert gas interface. The tube wall is provided with an outlet to achieve uniform injection of inert gas. A baffle is provided on the inner side of the annular tube to assist in airflow guidance and strip protection.

[0015] In some embodiments, the baffle includes a fixed plate and a sliding plate. The sliding plate is slidable relative to the fixed plate and is provided with a first elastic structure. The sliding plate is provided with a high-temperature resistant scraper for cleaning impurities on the surface of the metal strip to avoid affecting the annealing quality.

[0016] Compared with the prior art, the present invention provides an annealing process and apparatus, which has the following beneficial effects.

[0017] 1. The annealing process of this invention, by precisely setting the low-temperature long-term annealing parameters of 370℃–390℃, combined with the layered furnace loading and segmented cooling process, and the temperature control and airflow circulation structure of the special annealing furnace device, can stably control the hardness of metal strip within the target range, solve the problem of large hardness fluctuation in traditional processes, and can adapt to the production needs of strips of different thicknesses.

[0018] 2. This invention eliminates the need for multiple machines to work together. Compared with the traditional high-temperature annealing process, it greatly simplifies the operation process, shortens the process cycle, improves batch-to-batch production consistency, and reduces production energy consumption and labor costs.

[0019] 3. This invention effectively avoids problems such as oxidation of metal strip, surface impurity residue, and adhesion damage by using the sealing structure of the annealing furnace device, airflow circulation components, and cleaning and anti-adhesion design, thus ensuring the surface quality and structural integrity of the strip. The process parameters can be flexibly adjusted according to the strip specifications, adapting to metal strips of different raw material roll diameters and thicknesses, with a wide range of applications, and can meet diverse production needs.

[0020] Other advantages, objectives and features of the invention will be set forth in part in the description which follows; and in part will be apparent to those skilled in the art upon examination of the following description; or may be learned from practice of the invention. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the outer cover of the present invention.

[0022] Figure 2 This is a schematic diagram of the structure of the inner cover of the present invention.

[0023] Figure 3 This is a schematic diagram of the structure of the second rotating component of the present invention.

[0024] Figure 4 This is a schematic diagram of the structure of the fixing plate of the present invention.

[0025] Figure 5 This is a schematic diagram of the structure of the first rotating component of the present invention.

[0026] Figure 6 This is a schematic diagram of the annular tube structure of the present invention.

[0027] Figure 7 For the present invention Figure 4 A magnified structural diagram of region A in the middle.

[0028] Figure 8 This is a schematic diagram of the slide of the present invention.

[0029] Figure 9 This is a schematic diagram of the material rack structure of the present invention.

[0030] Figure 10 This is a schematic diagram of the structure of the protruding part of the material tray frame of the present invention.

[0031] In the picture: 1. Base 1; 104. Material rack; 110. Outer plate; 120. Inner base 1; 121. First rotating component; 1211. First drive motor; 1213. Torque sensor; 2. Inner cover; 206. Annular tube; 210. Upper part; 220. Lower part; 230. Middle rotating part; 233. Gear ring; 240. Connecting rod; 250. Second rotating component; 251. Second drive motor; 253. Transmission gear; 280. Baffle ; 281, Fixed plate; 2811, Guide groove; 2812, First fixed plate; 2813, Second fixed plate; 2814, Second elastic structure; 282, Sliding plate; 2821, Guide rail; 283, First elastic structure; 285, High-temperature resistant scraper; 286, Rotating plate; 2861, Hinge shaft; 2862, Slide groove; 287, Hydraulic cylinder; 2871, Fixed end; 2873, Slider; 3, Outer cover; 100, Metal strip 100. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0033] Reference Figures 1 to 10 This invention discloses an annealing process, comprising the following steps: Step S1, Furnace Loading: Load the metal strip 100 with a hardness of 68–79 after quenching into the annealing furnace; specifically: arrange the metal strip 100 in layers according to its thickness, with a spacing of not less than 3 cm between layers. The specific number of layers is determined according to Table 1. Raw material roll diameter (mm) Raw material height (mm) number of floors ≤850 ≤35 4 ≤850 ≤55 3 ≤850 ≤100 2 ≤850 ≤230 1 Table 1 Correspondence between Furnace Loading Layers Step S2, Vacuum Inner Cover Installation and Vacuuming: A vacuum-inert gas alternating displacement process is performed inside the furnace to reduce the oxygen content. Specifically: remove oil and water residue from the sealing ring, install the vacuum inner cover (corresponding to inner cover 2 in the subsequent device), align the positioning pins, and tighten the nuts diagonally. Use a vacuum pump to evacuate the furnace pressure to -0.095 MPa, turn off the vacuum pump, and tighten the vacuum cover fixing nuts a second time. This step relies on the sealing structure of the device base 1, inner cover 2, and vacuum pump interface to achieve a sealed vacuum.

[0034] Step S3, Gas Replacement: Atmosphere replacement is performed by alternating between vacuuming and inert gas filling three times. Specific parameters are shown in Table 2. Number of permutations Vacuum pressure (MPa) Inert gas filling pressure (MPa) first -0.095 0.06 The second -0.095 -0.04 The third -0.095 0.06 Table 2 Gas Replacement Parameters Note: This step requires the use of the inert gas inlet and outlet ports reserved in the device base 1 and inner cover 2, and the annular pipe assembly 5 (subsequent device components) to achieve uniform replacement of inert gas and ensure a stable atmosphere inside the furnace.

[0035] Step S4, Low-Temperature Long-Term Annealing: Heat at 370℃–390℃ and hold for 10–14 hours. Specific parameters are determined according to the strip thickness as shown in Table 3. Thickness (mm) Temperature (°C) Heating time (h) Insulation time (h) Target hardness ＜0.8 390 3.5 14 39-45 0.8≤×≤1.5 380–385 3.5 11-12 40-45 ＞1.5 380–390 3.5 12 42-50 Table 3. Annealing Parameter Correspondence Table Note: Temperature control in this step is achieved through the heating element of the outer casing 3 of the device. The temperature and atmosphere uniformity inside the furnace are ensured by the fan 4, fan blade 402 and annular pipe assembly 5 to ensure that the annealing hardness of the metal strip meets the standard.

[0036] Step S5, Segmented Cooling: Step S51: After the heat preservation is completed, the heating cover (corresponding to the outer cover 3 of the device) is lifted off, and the cooling cover is covered for air cooling to reduce the temperature to 300℃. This step requires the outer cover 3 to be lifted by the lifting part 6 of the device. The air cooling efficiency is improved by the airflow circulation of the fan 4 and the fan blade 402.

[0037] Step S52: Open the manual valve for inert gas, fill the furnace with inert gas until the pressure inside the furnace reaches 0.09 MPa, and then close the valve. The inert gas is evenly filled through the inert gas inlet and outlet ports and the annular pipe assembly 5 to ensure stable pressure inside the furnace.

[0038] Step S53: When the temperature drops below 200℃, stop the air cooling and open the water cooling solenoid valve to perform water cooling until the temperature drops to ≤45℃; water cooling is achieved through the cooling water pipe integrated inside the device base 1, and the airflow circulation of the fan 4 accelerates the cooling.

[0039] Step S6, Unloading: Disconnect the cooling water interface, lift the cooling cover, evacuate to -0.095MPa, loosen the clamping nut, open the exhaust valve to make the pressure inside and outside the furnace equal, and lift the material rack (the material rack is used to place metal strip 100 in layers) through the lifting device 6.

[0040] Each step of this annealing process requires specific equipment structure support. In order to achieve the accurate and efficient implementation of the above process and ensure the 100% annealing quality of metal strip, the following discloses an annealing furnace device adapted to the entire process, as detailed in Examples 4-7. Example 1

[0041] Take 100 pieces of metal strip with an initial hardness of 72–75 after quenching and process it according to the following parameters: Number of furnace layers: 4 layers, with a layer spacing of 3cm; Gas replacement: Perform three alternating replacements as per Table 2; Annealing temperature: 390℃; Heating time: 3.5 hours; Insulation time: 12 hours; Cooling method: Air cooling to 300℃ → Inert gas filling to 0.09MPa → Water cooling to ≤45℃; Results: The average hardness after treatment was 40.2–45.3, which meets the requirement of ≤45. Example 2

[0042] Take 100 pieces of metal strip (1.0 × 50 mm) with an initial hardness of 70–76 after quenching, and process it according to the following parameters: Number of furnace layers: 3 layers, with a layer spacing of 3cm; Gas replacement: Perform three alternating replacements as per Table 2; Annealing temperature: 385℃; Heating time: 3.5 hours; Insulation time: 12 hours; Cooling method: Same as above; Results: The average hardness after treatment was 39.9–49.5, with the vast majority below 45. Example 3

[0043] Take 100 pieces of metal strip (1.5×50mm) with an initial hardness of 68–72 after quenching, and process it according to the following parameters: Number of furnace layers: 2 layers, with a layer spacing of 3cm; Gas replacement: Perform three alternating replacements as per Table 2; Annealing temperature: 380–390℃; Heating time: 3.5 hours; Insulation time: 11–12 hours; Cooling method: Same as above; Results: The average hardness after treatment was 42.2–50.2, which met the requirements.

[0044] Comparative Example 1 The same batch of materials was treated using a traditional high-temperature annealing process (temperature > 500℃, holding time 4-6h, single-stage air cooling). Results: Hardness fluctuation range: 52–65; Three annealing furnaces are required. Poor batch-to-batch consistency; The comparison shows that the annealing process of the present invention is significantly better than the traditional solution in terms of hardness control stability, equipment efficiency and process consistency. Moreover, the above advantages are achieved by relying on a special annealing furnace device. The specific structure of the device will be described in detail in subsequent embodiments 4-7. Example 4

[0045] The present invention also discloses an annealing furnace device, which is used throughout the entire process.

[0046] The device is configured as follows: During furnace loading (step S1), the metal strip 100 is placed on the base 1 of the device; the vacuum inner shroud hoisting (step S2), gas replacement (step S3), low-temperature annealing (step S4) and segmented cooling (step S5) are all completed inside the device; During the unloading process (step S6), the material rack is lifted out by the lifting components of the device.

[0047] The following is a detailed design of each component of the device and their connection relationships, all of which are adapted to the above process parameter requirements.

[0048] The device specifically includes: Base 1 is the basic load-bearing component of the entire annealing furnace device. It is located at the bottom of the device, placed horizontally on the ground, and fixed to the ground by expansion bolts to ensure that there is no shaking or displacement during the operation of the device. It is suitable for pressure change scenarios such as vacuuming and pressurization in the process.

[0049] The base 1 has an annular sealing groove at its top, with a high-temperature resistant sealing ring embedded inside. This groove is used to seal against the bottom of the inner cover 2, preventing gas leakage from the furnace and meeting the sealing requirements of step S2 (vacuuming) and step S3 (gas replacement). The upper surface of the base 1 has uniformly distributed positioning protrusions for placing material racks. These racks are used to layer metal strips 100, meeting the layering requirements of step S1 (furnace loading). The positioning protrusions ensure accurate placement of the material racks and prevent deviations in the spacing between layers. The base 1 has integrated cooling water pipes inside, with both ends extending to the outside of the base 1 and connecting to an external water cooling system. This is for the water cooling step in step S53. Additionally, a vacuum pump interface and an inert gas inlet / outlet interface are reserved on one side of the base 1, connecting to the vacuum pump and inert gas storage tank, respectively. This is for the vacuuming step in step S2, the gas replacement step in step S3, and the inert gas pressurization step in step S52.

[0050] The base 1 bears the weight of the entire device, including the inner cover 2, the outer cover 3, the metal strip 100, and the material rack, providing a stable installation foundation; it also seals the inner cover 2 to ensure the stability of the vacuum and gas atmosphere inside the furnace; and it integrates pipeline interfaces to provide equipment connection support for each step of the process.

[0051] The inner cover 2 is a cylindrical sealing structure made of high-temperature and corrosion-resistant stainless steel. It is located above the base 1, and the bottom of the cover is embedded in the annular sealing groove of the base 1, which fits tightly with the sealing ring to form a closed annealing space (i.e., the core area inside the furnace). The metal strip 100 and the material rack are placed inside the inner cover 2 to match all the core process steps from step S1 to step S5.

[0052] Specifically, the bottom of the inner cover 2 is sealed to the base 1 through a sealing groove and a sealing ring. Depending on the actual use, it can be selected whether to fix it with bolts. If bolts are not required, it can be easily hoisted and disassembled.

[0053] A vacuum pump interface and an inert gas inlet / outlet interface are provided on the top outer side of the inner cover 2, which are connected to the corresponding interfaces reserved in the base 1 through flexible pipes to realize the pipeline connection for vacuuming and gas replacement; a fan blade and a fan blade cover are installed on the top inner side of the inner cover 2, and a fan is installed on the top outer side; multiple sets of annular pipes 206 are fixedly installed on the inner wall of the inner cover 2; a lifting component is provided on the top of the inner cover 2 for hoisting and disassembly.

[0054] The inner casing 2 is used to form a closed annealing space, ensuring the stability of the vacuum and inert gas atmosphere inside the furnace, preventing external air from entering and causing 100% oxidation of the metal strip, and matching the atmosphere control requirements of steps S2 and S3; in addition, it supports the internal heating, stirring, and airflow circulation components, providing a stable internal environment for low-temperature annealing and segmented cooling; at the same time, it is suitable for high-temperature conditions below 390℃ in the process, ensuring structural stability and no deformation.

[0055] The outer cover 3 is a cylindrical double-layer structure, preferably an integrated design of heating cover and cooling cover. The outer cover 3 is made of high-temperature resistant material with excellent heat insulation performance. It is fitted on the outside of the inner cover 2, located above the base 1, and can be separated from the base 1 for easy hoisting. It has both heating and cooling functions and is suitable for switching between low-temperature annealing (step S4) and segmented cooling (step S5) in the process.

[0056] There is no fixed connection between the bottom of the outer cover 3 and the base 1; the position is switched by hoisting. During annealing in step S4, the outer cover 3 covers the outside of the inner cover 2; during cooling in step S5, the outer cover 3 is hoisted off and replaced with a cooling cover, or the outer cover 3 itself integrates a cooling structure.

[0057] A heating element (such as a heating wire) is installed between the two layers of the outer cover 3. The heating element is connected to an external temperature control system, which can accurately control the heating temperature within the range of 370℃–390℃ to match the low-temperature annealing temperature requirements of step S4. One side of the outer cover 3 is provided with an inert gas manual valve interface and a water-cooled solenoid valve interface, which are connected to the inert gas storage tank and the external water cooling system, respectively, for matching steps S52 and S53; the top of the outer cover 3 is also provided with a lifting component, which is consistent with the lifting component structure of the inner cover 2, for lifting by external special lifting equipment.

[0058] Additional notes regarding lifting components: Both inner cover 2 and outer cover 3 require lifting.

[0059] The inner cover 2 is used for the vacuum inner cover hoisting in step S2, that is, to hoist the inner cover 2 above the base 1, align it with the positioning pin and seal it, and disassemble the inner cover 2 after step S6 when it is taken out of the furnace, so as to facilitate the removal of the material rack. The outer cover 3 is used for the cooling step S51, that is, by lifting the outer cover 3, the cooling cover can be replaced or the inner cover 2 can be exposed for air cooling or disassembly during equipment maintenance. At the same time, the distance between the outer cover 3 and the inner cover 2 can be adjusted according to process requirements to assist in temperature control.

[0060] All lifting components adopt high-strength lifting lug structures, which are welded and fixed to the top of the cover and are compatible with the hooks of external special lifting equipment to ensure a smooth and safe lifting process.

[0061] The double-layered outer casing 3 provides an insulating environment for the inner casing 2, reducing heat loss during the annealing process and ensuring uniform temperature inside the furnace. This is used to match the temperature stability requirements of the low-temperature long-term annealing in step S4. At the same time, it can integrate heating and cooling related interfaces and components to achieve rapid switching between heating and cooling in the process. It also protects the inner casing 2 from the influence of the external environment on the atmosphere and temperature inside the furnace.

[0062] Among them, the set of components of the fan, fan blade and fan blade cover is used to realize the airflow circulation in the inner cover 2, to ensure uniform temperature and gas concentration in the furnace, and to meet the requirements of step S4 low temperature annealing (temperature uniformity), step S3 gas replacement (uniform gas distribution) and step S5 air cooling (uniform cooling).

[0063] Specifically, the fan is fixedly installed at the center of the outer top of the inner cover 2. It can be fastened to the mounting base on the top of the inner cover 2 by bolts. The fan blade cover is a cylindrical mesh structure, which is fixedly installed on the inner top of the inner cover 2 to completely enclose the fan blade. The fan blade cover is connected to the wall of the inner cover 2 by a bracket. The bracket is made of high temperature resistant material to ensure structural stability in the high temperature environment of annealing.

[0064] During operation, the fan drives the fan blades to rotate, generating a downward airflow. This airflow is dispersed through the mesh structure of the fan blade cover, ensuring a uniform distribution of inert gas and heat within the inner cover 2. This prevents localized overheating or underheating and ensures uniform hardness of the metal strip 100 after annealing, matching the requirement for stable hardness in this embodiment. In the air-cooling step, the fan blade rotation accelerates the airflow within the inner cover 2, working in conjunction with the cooling cover to achieve rapid cooling to 300°C, matching the air-cooling requirements of step S51. During the gas replacement process, the airflow circulation accelerates the replacement of air and inert gas within the furnace, shortening the replacement time and ensuring that the oxygen content drops to the required range, matching the atmosphere control in steps S2 and S3.

[0065] Regarding the overall assembly of the upper annular tube a, lower annular tube b, and connectors, the annular tube 206 assembly is used to assist in airflow circulation and uniform temperature distribution, while also assisting in fixing the 100 coils of metal strip. This is adapted to the furnace loading layering requirements in step S1 and the annealing temperature uniformity requirements in step S4. Specifically, it is configured with three sets of annular tubes 206, each corresponding to one of the three layers of wound metal strip 100. If the furnace loading layer count is four layers, an additional set of annular tubes 206 can be added to accommodate the changes in the furnace loading layer count as shown in Table 1 above.

[0066] All three sets of annular tubes 206 are fixedly installed on the inner wall of the inner cover 2 and are evenly distributed along the height direction of the inner cover 2. Each set of annular tubes 206 corresponds to the height of a layer of metal strip 100, and the distance between the annular tubes 206 and the strip is consistent. Each set of annular tubes 206 consists of an upper annular tube a and a lower annular tube b. The upper annular tube a is located above the corresponding layer of strip, and the lower annular tube b is located below the corresponding layer of strip. The two are arranged in parallel and are coaxial with the inner cover 2. Preferably, a connector is provided between the upper annular tube a and the lower annular tube b. Specifically, multiple sets of rotating wheels are installed at equal intervals on the inner sidewalls of the upper annular tube a and the lower annular tube b. The rotating wheels are connected to the wall of the annular tube 206 through a rotating shaft and can rotate freely. The connector is an annular sleeve, which is fitted into the gap in the middle of the rotating wheel. The inner diameter of the annular sleeve matches the gap in the middle of the rotating wheel, and the outer diameter is slightly smaller than the inner diameter of the 100 rolls of metal strip.

[0067] Specifically, both the upper annular pipe a and the lower annular pipe b are connected to the inert gas interface at the top of the inner cover 2 through branch pipes. Small gas outlets are evenly arranged on the pipe wall of the annular pipe 206. The inert gas can enter the annular pipe 206 through the branch pipes and then be evenly sprayed into the interior of the inner cover 2 through the gas outlets. The annular pipe 206 is made of high temperature and corrosion resistant stainless steel. The branch pipes are welded to the annular pipe 206 for sealing and preventing leakage.

[0068] The annular tube 206 assembly, by uniformly spraying inert gas through the outlet of the annular tube 206, combined with the airflow circulation of the blower and fan blades, makes the inert gas distribution in the furnace more uniform, avoids local oxygen residue, and accelerates heat transfer to ensure that the temperature of each strip layer is consistent, in order to match the uniformity requirements of gas replacement in step S3 and annealing in step S4. When using this device, during the vacuuming stage of step S2, the external vacuum pump is started, and the air inside the inner cover 2 is extracted through the vacuum pump interface on the top of the base 1 and the inner cover 2. The air inside the inner cover 2 is discharged to the outside through the air outlet of the annular pipe 206 (auxiliary air extraction to accelerate air discharge), the vacuum pump interface at the top of the inner cover 2, the flexible pipeline and the vacuum pump. When the gas pressure inside the furnace drops to -0.095MPa, the vacuum pump is turned off, and the sealing structure of the inner cover 2 is tightened again to complete the vacuuming. At this time, the inner cover 2 is in a low-pressure, low-oxygen environment, and the airflow stops.

[0069] In step S3, the gas replacement stage, there are three alternating vacuuming and inert gas filling processes.

[0070] Taking a single replacement as an example, the three processes are the same, only the gas filling pressure is different (according to the parameters in Table 2): The vacuum pump is restarted to pump the gas pressure inside the inner cover 2 to -0.095MPa and discharge the residual air; the vacuum pump is turned off and the valve of the inert gas storage tank is opened. The inert gas is evenly sprayed into the interior of the inner cover 2 through the inert gas interface of the base 1 and the inner cover 2, the branch pipes, each group of annular pipes 206, and the outlet of the annular pipe 206; at the same time, the fan is started to drive the fan blades to rotate. The fan blades disperse the airflow through the fan blade cover, so that the injected inert gas circulates quickly in the inner cover. The airflow direction is: outlet of annular pipe 206 → fan blades blowing downward → covering each layer of metal strip 100 → top space of inner cover 2 → fan blades sucking in → dispersing downward again, forming a closed loop circulation; When the gas pressure inside the furnace reaches the charging gas pressure corresponding to the number of replacement cycles (0.06MPa for the first time, -0.04MPa for the second time, and 0.06MPa for the third time), close the inert gas valve to complete a single replacement; repeat the above steps three times until the oxygen content inside the furnace drops to the process requirements, the airflow circulation stops, and the blower is turned off.

[0071] In step S4, the low-temperature annealing stage, the heating element of the outer casing 3 is activated to begin heating, with the target temperature controlled at 370℃–390℃ (according to the parameters in Table 3). Simultaneously, the fan is activated to drive the fan blades to rotate, forming a closed-loop airflow circulation. The airflow direction is as follows: the fan blades blow air downwards → passing through each layer of metal strip 100 → absorbing the heat generated by heating → flowing through the annular pipe 206 (the annular pipe 206 does not emit inert gas and only serves as an airflow guide component) → returning to the top of the fan blades and being transported downwards again by the fan blades. The annular pipe 206 assists in dispersing the airflow, ensuring that the airflow evenly covers each layer of strip, making the temperature of each layer of strip consistent, and avoiding local overheating or failure to reach the annealing temperature. Throughout the annealing process, the airflow continues to circulate until the heat preservation ends, at which point the heating element and the fan are turned off.

[0072] In the segmented cooling stage of step S5, specifically in step S51 (air cooling stage), the outer cover 3 is opened, the cooling cover is closed, the fan is started, and the fan blades are driven to rotate. The airflow direction is the same as in the annealing stage (closed-loop circulation). At this time, the cooling cover absorbs the heat of the inner cover 2, and the airflow carries the heat out of the inner cover 2, accelerating the cooling down until the temperature drops to 300℃, at which point the fan stops. In step S52 (inert gas pressurization stage), the inert gas manual valve is opened, and the inert gas is evenly sprayed into the inner cover 2 through the outlet of the annular pipe 206. The airflow direction is: annular pipe 206 → inside the inner cover 2 → filling the entire space until the furnace pressure reaches 0.09MPa. The valve is then closed, and the airflow stops (pressurization can prevent external air from entering during the cooling process and also helps stabilize the strip performance). In step S53, during the water cooling stage, the external water cooling system is started, and the cooling water circulates through the cooling pipes inside the base 1. At the same time, the fan is started, and the airflow circulates again. The airflow direction is: the fan blades blow air downwards → flow over the strip and above the base 1 → absorb the heat carried away by the cooling water → circulate and dissipate heat until the temperature drops to ≤45℃. Then, the water cooling system and the fan are turned off, and the cooling is completed.

[0073] This annealing furnace apparatus is strictly matched with the above-mentioned annealing process, including: the sealing structure (sealing ring of base 1, sealing of inner cover 2) is adapted to the vacuum degree and atmosphere requirements of step S2 vacuuming and step S3 gas replacement; the heating and temperature control components (heating element of outer cover 3, temperature control system) are adapted to the temperature range of step S4 low-temperature annealing; the cooling components (cooling cover, water-cooled pipe, fan) are adapted to the temperature requirements and cooling rate of step S5 segmented cooling; the annular pipe 206, fan, and fan blades are adapted to the airflow circulation and uniformity requirements of each step; the lifting components are adapted to the lifting requirements of each cover and match the operation steps of steps S2, S5, and S6; and the pipelines and interfaces are adapted to the connection of vacuum pump, inert gas storage tank, and water cooling system to ensure smooth connection of each step of the process, ultimately achieving the goal of controlling the hardness of metal strip 100 within the range of 40±5, consistent with the results of the embodiment. Example 5

[0074] This embodiment is a further improvement on the annealing furnace device in Embodiment 4 above. In the actual annealing process, the following technical problems exist: First, during the annealing process, the multi-layered stacked metal strip 100 is prone to uneven heating due to the different distances between each layer and the heat source. The strip closer to the heat source has a higher temperature, while the strip farther from the heat source has a lower temperature, affecting the uniformity of hardness after annealing. Second, during rolling, slitting, and transportation, the surface of the metal strip 100 may be contaminated with oil, scale, or other impurities. These impurities may affect the surface quality of the strip during annealing, and may even lead to abnormal local hardness. Third, after annealing, the metal strip 100 is prone to sticking to the material rack 104 due to uneven thermal expansion and cooling contraction, leading to difficulties in unloading from the furnace and even damage to the strip.

[0075] To address the aforementioned technical problems, the annealing furnace apparatus has been improved in this embodiment as follows.

[0076] The base 1 includes an outer plate 110 and an inner base 120. The outer plate 110 is a fixed structure, and its bottom is fixedly connected to the ground by expansion bolts. An annular slide rail is provided on the top of the outer plate 110. The inner base 120 is a rotatable structure, and a first rotating component 121 is provided at the bottom of the inner base 120. The first rotating component 121 can be installed inside the outer plate 110.

[0077] Specifically, the first rotating component 121 includes a first drive motor 1211 and a first reducer. The output end of the first drive motor 1211 is connected to the input end of the first reducer. The output end of the first reducer is provided with a gear, and the output end of the first reducer is meshed with the outer rack of the inner base 120 in the circumferential direction through the gear.

[0078] Optionally, the bottom of the inner base 120 is provided with an annular slider that mates with an annular slide rail. The annular slider is embedded in the annular slide rail and can rotate along the annular slide rail. The inner base 120 is rotatably mounted above the outer disk 110 through the cooperation of the annular slider and the annular slide rail.

[0079] A material rack 104 is provided on the top of the inner base 120, which is used to support the coiled metal strip 100. The material rack 104 is placed in the middle of the inner base 120.

[0080] The function of the first rotating component 121 is that, during the low-temperature annealing heating process in step S4, the first drive motor 1211 drives the inner base 120 to rotate slowly through the first reducer. The inner base 120 drives the material plate frame 104 and the metal strip 100 on it to rotate synchronously, so that each part of the metal strip 100 receives the radiant heat from the heating element of the outer cover 3 evenly, avoiding uneven heating caused by fixed position, thereby improving the uniformity of hardness after annealing.

[0081] Optionally, a heat-absorbing and heat-dissipating coating is provided on the outer side of the outer casing 3. The heat-absorbing and heat-dissipating coating is uniformly coated on the outer surface of the outer casing 3, and the coating material can be a high-emissivity ceramic coating (preferably a black chrome coating or an alumina coating).

[0082] The function of the heat-absorbing and heat-dissipating coating is that, in the heating stage of step S4, the coating can quickly absorb the heat generated by the heating element and transfer it to the inner cover 2; in the cooling stage of step S5, the coating can quickly radiate the heat emitted by the inner cover 2 to the external environment, thereby improving heating and cooling efficiency and shortening the process cycle.

[0083] Optionally, the outer surface of the inner cover 2 is configured as a curved surface. Specifically, the curved surface is a wavy surface, evenly distributed along the circumference of the inner cover 2. The wave height can be selected as 5-15mm, and the wavelength can be selected as 30-50mm. The function of the curved surface structure is to increase the outer surface area of ​​the inner cover 2, which can improve the heat absorption efficiency during the heating stage and the heat dissipation efficiency during the cooling stage, further shortening the process cycle and reducing energy consumption.

[0084] The inner cover 2 is divided into an upper part 210, a lower part 220, and a middle rotating part 230. The upper part 210 and the lower part 220 are fixedly connected by a connecting rod 240, and the upper part 210 and the lower part 220 remain fixed relative to the base 1.

[0085] The middle rotating part 230 is disposed between the upper part 210 and the lower part 220. The upper end of the middle rotating part 230 is rotatably connected to the lower end of the upper part 210 through a first slewing bearing, and the lower end of the middle rotating part 230 is rotatably connected to the upper end of the lower part 220 through a second slewing bearing.

[0086] A second rotating component 250 is provided on the outer side of the middle rotating part 230. The second rotating component 250 can be optionally installed on the upper part 210 of the inner cover 2 or the outer cover 3. Specifically, the second rotating component 250 includes a second drive motor 251, a second reducer, and a transmission gear 253. The output end of the second drive motor 251 is connected to the input end of the second reducer, and the output end of the second reducer is fixedly connected to the center of the transmission gear 253. The transmission gear 253 meshes with a gear ring 233 provided on the outer side of the middle rotating part 230.

[0087] When the middle layer rotating part 230 needs to rotate, the second drive motor 251 drives the transmission gear 253 to rotate through the second reducer. The transmission gear 253 drives the middle layer rotating part 230 to rotate around the axis of the inner cover 2 through the gear ring 233.

[0088] Optionally, the sealing between the middle rotating part 230 and the upper part 210 and the lower part 220 is achieved by providing a first seal and a second seal on the outer side of the first slewing bearing and the second slewing bearing, respectively. The first seal and the second seal are preferably magnetohydrodynamic seals, in order to ensure that the vacuum and atmosphere inside the inner cover 2 are not affected by rotation.

[0089] A baffle 280 is provided on the inner side of the annular tube 206. The baffle 280 includes a fixed plate 281 and a sliding plate 282. The fixed plate 281 is fixedly connected to the inner wall of the annular tube 206, and the fixed plates 281 are evenly distributed along the circumference of the annular tube 206, with four or more being preferred.

[0090] The sliding plate 282 is slidably mounted on the inner side of the fixed plate 281. Specifically, the inner side of the fixed plate 281 is provided with a guide groove 2811, and the outer side of the sliding plate 282 is provided with a guide rail 2821 that cooperates with the guide groove 2811. The sliding plate 282 is embedded in the guide groove 2811 through the guide rail 2821 and can slide within the guide groove 2811. A first elastic structure 283 is provided between the fixed plate 281 and the sliding plate 282. The first elastic structure 283 is a compression spring or a disc spring. One end of the first elastic structure 283 abuts against the fixed plate 281, and the other end abuts against the sliding plate 282, and is used to provide a restoring force for the sliding plate 282.

[0091] A pressure sensor may be provided between the sliding plate 282 and the first elastic structure 283. The pressure sensor is fixedly installed on the inner side of the sliding plate 282 and is used to detect the contact pressure between the sliding plate 282 and the metal strip 100.

[0092] The sliding plate 282 is also equipped with a high-temperature resistant scraper 285. The high-temperature resistant scraper 285 is made of stainless steel wire brush or high-temperature resistant fiber brush and is used to contact the surface of the metal strip 100 to scrape off impurities.

[0093] Under normal conditions, the baffle 280 serves as both insulation and airflow guide, reducing radiant heat loss. Before annealing (at room temperature) or after annealing (after cooling to a low temperature), a high-temperature resistant scraper 285 contacts the outer surface of the metal strip 100. Then, driven by the second rotating component 250 on the middle rotating part 230, or by the first rotating component 121 on the inner base 120, the surface of the metal strip 100 is cleaned by the high-temperature resistant scraper 285, removing oil, scale, and other impurities. The high-temperature resistant scraper 285 can cover the surface of the metal strip 100.

[0094] During this process, the contact pressure can be detected in real time by the pressure sensor. When the pressure value exceeds the preset threshold, it indicates that there are large particulate impurities or protrusions on the surface of the metal strip 100. The system can automatically control the middle layer rotating part 230 to reciprocate and enhance the scraping effect. Example 6

[0095] This embodiment is a further improvement on Embodiment 5. However, the following technical problems still exist during the actual annealing process: After annealing, the metal strip 100 is prone to sticking to the material rack 104 or the material rack 104 due to uneven thermal expansion and cooling contraction. Traditional separation methods often involve manual tapping or prying, which can easily damage the strip edges and affect product quality. To solve the above technical problems, this embodiment further improves the structure of the baffle 280.

[0096] The fixing plate 281 of the baffle 280 is divided into two parts: a first fixing plate 2812 and a second fixing plate 2813. The first fixing plate 2812 is fixedly connected to the inner wall of the annular tube 206. The second fixing plate 2813 is disposed inside the first fixing plate 2812, and a second elastic structure 2814 is provided between the second fixing plate 2813 and the first fixing plate 2812. The second elastic structure 2814 is a compression spring or a disc spring, one end of which abuts against the first fixing plate 2812, and the other end of which abuts against the second fixing plate 2813. A sliding plate 282 is slidably mounted on the second fixing plate 2813, and a first elastic structure 283 (same as in embodiment 5) is provided between the sliding plate 282 and the second fixing plate 2813.

[0097] A rotating plate 286 is rotatably connected to the inner side of the sliding plate 282. Specifically, one end of the rotating plate 286 is rotatably connected to the inner end of the sliding plate 282 via a hinge shaft 2861, and the rotating plate 286 can rotate around the hinge shaft 2861.

[0098] A hydraulic cylinder 287 is connected to the rotating plate 286. The fixed end 2871 of the hydraulic cylinder 287 is fixedly connected to the middle rotating part 230 of the inner cover 2, and the telescopic end of the hydraulic cylinder 287 is slidably connected to the middle part of the rotating plate 286. Specifically, a sliding groove 2862 is provided in the middle part of the rotating plate 286, and a slider 2873 is provided on the telescopic end of the hydraulic cylinder 287. The slider 2873 is embedded in the sliding groove 2862 and can slide along the sliding groove 2862. By controlling the extension length of the telescopic end by the hydraulic cylinder 287, the rotation angle of the rotating plate 286 can be controlled: when the telescopic end of the hydraulic cylinder 287 is fully retracted, the rotating plate 286 is in a retracted state and parallel to the sliding plate 282. At this time, the rotating plate 286 does not contact the metal strip 100.

[0099] Additionally, the retraction of the hydraulic cylinder 287 at this time allows the rotating plate 286 to drive the second fixed plate 2813 to press the second elastic structure 2814, preventing the high-temperature resistant scraper 285 from contacting the metal strip 100. This can be used during the metal strip 100 loading stage to avoid the high-temperature resistant scraper 285 obstructing the loading of the metal strip 100; it also prevents the high-temperature resistant scraper 285 from uncontrollably scraping the surface of the metal strip 100. When the telescopic end of the hydraulic cylinder 287 extends to the first position L1, the rotating plate 286 rotates outward around the hinge axis 2861, and the free end of the rotating plate 286 contacts the outer surface of the metal strip 100. As the hydraulic cylinder 287 continues to apply pressure, the rotating plate 286 presses the metal strip 100, giving it a tendency to move. The material rack 104 extends outward with a protrusion. The protrusion is only provided at one end of the material rack 104 (i.e., one side edge of the material rack 104), and there are no protrusions on the other edges. The protrusion is flat or L-shaped and is integrally formed or welded to the material rack 104.

[0100] When the telescopic end of the hydraulic cylinder 287 extends to the second position L2 (the second position L2 is smaller than the first position L1), as the first rotating component 121 drives the inner base 120, the protrusion on one side of the material rack 104 contacts the free end of the rotating plate 286 away from the fixed plate 281. Subsequently, under the drive of the first rotating component 121 on the metal strip 100, or under the drive of the second rotating component 250 on the middle rotating part 230, the rotating plate 286 applies an outward pressing force to the metal strip 100, causing the metal strip 100 to deviate slightly, thereby separating from the upper surface of the material rack 104 and avoiding adhesion.

[0101] Since the protrusion is only located at one end of the material rack 104, and there are no protrusions on the other three sides, the rotating plate 286 can directly contact the metal strip 100 in the area without protrusions to achieve extrusion displacement of the metal strip 100; while in the area with protrusions, the rotating plate 286 can push the protrusions to push the material rack 104. The two methods do not conflict with each other and can be selected as needed.

[0102] As a supplement, when the extension length of the extension end of the hydraulic cylinder 287 is controlled at the third position L3, that is, when the extension end of the hydraulic cylinder 287 is fully retracted, the free end of the rotating plate 286 does not make contact with the protrusion of the material plate holder 104 or the metal strip 100.

[0103] The cleaning process is as follows (before annealing or after cooling): Before annealing begins (at room temperature) or after annealing and cooling to ≤45℃, the rotating plate 286 is retracted by the hydraulic cylinder 287, and the metal strip 100 is only contacted by the high-temperature resistant scraper 285 on the sliding plate 282; the middle layer rotating part 230 is started, which drives the annular tube 206 and the baffle 280 to rotate, and the high-temperature resistant scraper 285 scrapes and cleans the surface of the metal strip 100; the pressure sensor detects the contact pressure, and when abnormal pressure is detected, the second rotating part 250 controls the middle layer rotating part 230 to reciprocate, thereby enhancing the cleaning effect.

[0104] The anti-adhesion process is as follows (cooling stage): During the segmented cooling process in step S5, when the temperature drops to 100-200℃ (at this time, the metal strip 100 has a certain strength, and extrusion will not cause deformation, but it has not been completely cooled, and the adhesion has not been completely cured), the rotating plate 286 is extended to the first position L1 or the second position L2 by the hydraulic cylinder 287; depending on the adhesion situation, the protrusion of the metal strip 100 or the material plate 104 is pushed; at the same time, the first rotating component 121 of the inner base 120 is activated, so that the metal strip 100 or the material plate 104 are displaced relative to each other, and separation is achieved.

[0105] Optionally, in the auxiliary heating during the annealing process, during the low-temperature annealing process in step S4, the baffle 280 can be slowly rotated back and forth by the middle layer rotating part 230. The rotation of the baffle 280 can disturb the airflow in the inner cover 2, break the possible laminar boundary layer, enhance the convective heat transfer effect, and further improve the temperature uniformity.

[0106] It should be noted that during the anti-adhesion operation, the pressure sensor alone cannot determine whether the metal strip 100 has shifted. This is because when the hydraulic cylinder 287 drives the rotating plate 286 to extend to the first position L1 (i.e., the rotating plate 286 contacts the outer surface of the metal strip 100 and applies pressure), the pressure applied by the rotating plate 286 to the metal strip 100 is transmitted through the rotating plate 286 and the sliding plate 282 to the first elastic structure 283 and the second elastic structure 2814. At this time, both the first elastic structure 283 and the second elastic structure 2814 are in a compressed state. The pressure value detected by the pressure sensor installed inside the sliding plate 282 is the superposition of several forces: the pressure applied by the rotating plate 286 to the metal strip 100, the elastic reaction force generated by the compression of the first elastic structure 283, the elastic reaction force generated by the compression of the second elastic structure 2814, and the resistance generated by the sliding friction between the sliding plate 282 and the fixed plate 281.

[0107] In this state, even if the metal strip 100 has successfully separated from the material rack 104 and shifted, the squeezing force of the rotating plate 286 on the metal strip 100 has not been eliminated. The first elastic structure 283 and the second elastic structure 2814 remain compressed, and the pressure sensor reading remains high, making it impossible to accurately determine whether the separation was successful based on the decrease in pressure. Simultaneously, when the hydraulic cylinder 287 continues to apply pressure, the first elastic structure 283 and the second elastic structure 2814 are further compressed, and the pressure value detected by the pressure sensor continues to increase. However, at this time, the metal strip 100 may not have shifted yet, only exhibiting compression of the elastic structures. The pressure sensor struggles to distinguish between the compressed elastic structures and the shifted metal strip 100.

[0108] As an optional detection method, or as a supplement to the detection method, a torque sensor 1213 can be provided at the drive end of the first rotating component 121. The torque sensor 1213 is installed at the output end of the first drive motor 1211 or the output end of the first reducer, and is used to detect the torque value when the inner base 120 rotates in real time.

[0109] The torque sensor 1213 operates on the principle that when the rotating plate 286 applies pressure to the metal strip 100, if a relative displacement occurs between the metal strip 100 and the material holder 104, the rotational resistance of the inner base 120 changes, causing a sudden change in the torque value detected by the torque sensor 1213. Specifically, when the metal strip 100 is adhered to the material holder 104, the inner base 120 needs to output a large driving torque to rotate the metal strip 100. When the metal strip 100 successfully separates from the material holder 104, the contact between them disappears or transforms into low-resistance rolling friction, and the driving torque of the inner base 120 decreases significantly. By monitoring the change in torque value from the initial value R1 to R2, the success of the separation operation can be accurately determined.

[0110] In cleaning mode, the detection value of the pressure sensor is the main basis for judgment, while in anti-adhesion mode, the detection value of the torque sensor 1213 is the main basis for judgment. Example 7

[0111] This embodiment is a further supplement to Embodiments 5 and 6. An auxiliary guide plate (not shown in the figure) can be provided between two adjacent baffles 280 on the inner side of the annular pipe 206.

[0112] The auxiliary guide vane does not cover the air outlet on the annular pipe 206. Optionally, the auxiliary guide vane is located between two adjacent air outlets, or above or below the air outlets, to ensure that the gas ejected from the air outlets is not blocked.

[0113] The auxiliary guide plate is an arc-shaped plate, which is fixedly connected to the inner wall of the annular pipe 206. The width of the auxiliary guide plate is smaller than the width of the baffle 280.

[0114] Multiple guide holes can be opened on the auxiliary guide plate, and the diameter of the guide holes gradually increases along the airflow direction to form a nozzle structure.

[0115] The auxiliary guide plate serves to further guide the airflow direction during the low-temperature annealing in step S4 and the cooling in step S5, so that the airflow flows more concentratedly to the surface of the metal strip 100, thereby improving the heat exchange efficiency; the gradually expanding structure of the guide hole can accelerate the airflow and enhance the convective heat transfer effect.

[0116] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0117] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. An annealing process characterized by, Includes the following steps: Step S1: Load the metal strip (100) with a hardness of 68–79 after quenching into the annealing furnace device. Step S2: Perform vacuum-inert gas alternating replacement in the furnace to reduce the oxygen content in the furnace; Step S3: Heat and hold at a temperature range of 370℃–390℃ for 10–14 hours; Step S4: Cool the temperature to ≤45℃ in stages using air cooling, inert gas pressurization, and water cooling in sequence; Step S5: Finally, the hardness of the strip (100) is controlled within the range of 40±5.

2. The annealing process of claim 1, wherein, When the thickness of the metal strip (100) is 0.8 mm, the annealing temperature is 390℃, the holding time is 12–14 hours, and the hardness drops to 39–45.

3. The annealing process of claim 1 wherein, When the thickness of the metal strip (100) is 0.9–1.0 mm, the annealing temperature is 380–385 °C, the holding time is 11–12 hours, and the hardness drops to 40–45.

4. The annealing process of claim 1 wherein, When the thickness of the metal strip (100) is 1.5 mm, the annealing temperature is 380–390℃, the holding time is 11–12 hours, and the hardness drops to 42–50.

5. An annealing furnace apparatus adapted to the annealing process of claim 1, characterized by It includes a base (1), an inner cover (2) and an outer cover (3). The base (1) is used to provide a stable installation foundation and to achieve sealing and pipeline connection. The inner cover (2) is used to form a closed annealing space. The outer cover (3) is used to achieve heating and heat preservation functions. The three work together to adapt to each step of the annealing process.

6. The annealing furnace installation according to claim 5, characterized in that The base (1) is horizontally fixed to the ground. The top is provided with an annular sealing groove and a positioning protrusion. A high-temperature resistant sealing ring is embedded in the sealing groove to ensure the sealing performance inside the furnace. The positioning protrusion is used to position the material rack (104) that carries the metal strip (100). The base (1) integrates cooling water pipes and reserves a vacuum pump interface and an inert gas inlet / outlet interface, which are adapted to water cooling, vacuuming and gas replacement steps respectively.

7. The annealing furnace apparatus according to claim 5, characterized in that, The inner cover (2) is a sealed structure made of high temperature and corrosion resistant material. The bottom is sealed to the base (1). The top is equipped with a lifting device, a vacuum pump interface and an inert gas inlet / outlet interface. The inner side is equipped with an annular pipe (206) for airflow circulation and uniform gas distribution to ensure the uniformity of annealing atmosphere and temperature.

8. The annealing furnace apparatus according to claim 5, characterized in that, The outer cover (3) is fitted on the outside of the inner cover (2). It is made of heat-insulating and high-temperature resistant material and has a heating element inside. The heating element is connected to an external temperature control system to accurately control the annealing temperature at 370℃–390℃. The outer cover (3) is equipped with corresponding interfaces and lifting parts to adapt to cooling steps and hoisting operations.

9. The annealing furnace apparatus according to claim 7, characterized in that, The annular tube (206) is distributed along the height direction of the inner cover (2) and connected to the inert gas interface. The tube wall is provided with an outlet to achieve uniform injection of inert gas. The inner side of the annular tube (206) is provided with a baffle (280) to assist in airflow guidance and protection of the strip (100).

10. The annealing furnace apparatus according to claim 9, characterized in that, The baffle (280) includes a fixed plate (281) and a sliding plate (282). The sliding plate (282) can slide relative to the fixed plate (281) and is provided with a first elastic structure (283). The sliding plate (282) is provided with a high-temperature resistant scraper (285) for cleaning impurities on the surface of the metal strip (100) to avoid affecting the annealing quality.

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