A forging hot precision cutting forming method of a track link of a construction machine

Abstract

The present application relates to the field of engineering machinery track walking system parts forging processing technology, especially to a kind of engineering machinery dry track chain track joint's hot forging precision cutting forming method, comprising the following steps: S1, blank gradient heating homogenization treatment;S2, continuous die forging near net forming;S3, multi-dimensional residual heat working condition parameter acquisition;S4, residual heat temperature field determination and grade division;S5, graded differential constant temperature stress release correction;S6, working condition self-adaptive precision cutting parameter dynamic matching;S7, integrated hot forging precision cutting near net forming;S8, residual heat window locking type quenching and tempering shaping.The present application obtains blank temperature field, residence time and environmental heat dissipation condition by multi-dimensional residual heat working condition acquisition, after residual heat working condition grade is determined by core-surface temperature difference and residual stress double-factor grading, according to grade matching differential constant temperature release process, core-surface temperature difference is reduced and pre-existing residual stress is released, so that blank is completed integrated precision cutting under the condition of matching with its hot plasticity.

Description

Technical Field

[0001] This invention relates to the field of forging and processing technology for components of engineering machinery track walking systems, and in particular to a method for hot forging and precision cutting of dry track links for engineering machinery. Background Technology

[0002] Dry track links are the core load-bearing components of the chassis walking mechanism of construction machinery such as excavators and bulldozers. Dozens of links are connected in series to form the track chain, which bears the weight of the whole machine, ground impact and alternating meshing load of the drive wheel for a long time. The dimensional accuracy and surface texture of the tread and nut mounting surface directly determine the walking stability and service life of the whole machine.

[0003] As construction machinery develops towards medium and large tonnage and high operational intensity, the production of track links continues to rise, and the requirements for near-net-shape forming degree and batch consistency of forged blanks are becoming increasingly stringent.

[0004] Current dry track link systems generally employ a process of heating bar stock, pre-forging, final forging, air cooling, followed by flash trimming, CNC milling of the tread and nut mounting surfaces, heat treatment, and subsequent hole machining. Some production lines attempt to reduce milling allowance by hot-trimming the edges using residual heat after final forging; however, hot trimming only removes the outer flash, and the tread and nut mounting surfaces still rely on subsequent cold milling to ensure dimensional accuracy.

[0005] However, the above process has the following problems in the mass continuous forging production of dry track link sections:

[0006] First, intermittent production line restarts, cross ventilation in the low-temperature workshop during night shifts, and uneven localized air cooling and insulation within the material handling frames all lead to undesigned temperature gradients between the surface and core of the blanks, with significant differences in temperature drop rates between different batches and at different times. Existing processes cannot adapt to this temperature field dispersion, resulting in inconsistent surface metal springback after hot cutting, and the exposure of defects such as convex surfaces and excessive flatness after cold machining, leading to large fluctuations in batch yield.

[0007] Secondly, during the temporary storage process, the blanks undergo non-standard hot and cold alternation in some areas, resulting in alternating tempering softening and work hardening. When entering the precision cutting process, the cutting stress and the pre-stored residual stress are coupled, producing irregular twisting deformation. Conventional shaping processes are difficult to correct this, and it is often not discovered until the subsequent machining or even assembly stages, resulting in a double waste of time and materials.

[0008] Therefore, it is necessary to design a new dry track link forging hot precision cutting method to improve the near-net-shape forming accuracy and batch consistency of the blank, and reduce subsequent machining costs. Summary of the Invention

[0009] To solve one of the aforementioned technical problems, the present invention employs the following technical solution: a forging and hot-cutting method for dry track link components of engineering machinery, comprising the following steps:

[0010] S1. Gradient heating and homogenization treatment of billet;

[0011] S2. The heated billet is pre-forged and shaped, and then forged and filled to obtain a dry track link blank with a complete outline and retaining the high temperature residual heat of forging.

[0012] S3. Immediately after the final forging is completed, acquire multiple parameters such as billet temperature, dwell time after final forging, workshop ambient temperature and humidity, and convection wind speed to obtain the original temperature field data of the billet caused by production intervals, ambient cooling, and stacking heat dissipation disturbances.

[0013] S4. Based on the acquired parameters and the pre-calibrated temperature drop history and the corresponding relationship with the surface residual stress, determine the real-time waste heat temperature field distribution of the blank, determine the core-surface temperature difference gradient and the degree of surface residual stress accumulation, and then classify the blank into different waste heat working condition levels.

[0014] S5. For blanks with different waste heat conditions, a homogeneous heat preservation and slow release process with corresponding duration and temperature threshold is matched to make the overall temperature field and stress field of the blank tend to be homogeneous and steady state.

[0015] S6. Adaptive Precision Cutting Parameter Dynamic Matching: Based on the residual heat condition level of the blank determined in S4, dynamically retrieve the precision cutting stamping speed, cutting feed, die preheating compensation temperature and holding time that match the level.

[0016] S7. Before the blank temperature drops below the critical temperature for phase transformation and within the range of high-temperature plastic stability, use the matched dynamic process parameters to simultaneously complete the flash removal, tread precision cutting, and hot shaping of the nut mounting surface in one go.

[0017] S8. After the precision cutting is completed, the residual heat temperature window of the blank is locked instantly, and the residual heat treatment process is immediately started to achieve batch consistency of the forming accuracy, metallographic structure and mechanical properties of the track link under different disturbance conditions.

[0018] Preferably, the gradient heating and homogenization treatment of the billet is performed by a walking beam furnace, specifically including the following steps:

[0019] For furnace loading and arrangement, the operator lays the sawn bar billets of fixed length in a single layer on the feeding platform, with a spacing of ≥20mm between billets. The length direction of the billets is perpendicular to the movement direction of the walking beam in the furnace. The arranged billets are then fed onto the heat-resistant steel fixed beam in the preheating section of the walking beam furnace.

[0020] Preheating is carried out by controlling the stepping cycle of the walking beam to ensure that the average heating rate of the billet in the preheating section is ≤150℃ / h, heating the billet from room temperature to 850℃~950℃, and holding it in this temperature range for 20min~40min to ensure that the temperature difference of the billet cross section is ≤50℃.

[0021] The billet is gradually moved to the heating section by the walking beam inside the furnace chamber of the walking beam heating furnace. By controlling the walking beam's walking cycle, the average heating rate of the billet in the heating section is ≤250℃ / h. It continues to rise to 1180℃~1220℃ and is held in this forging temperature range for 15min~30min to make the temperature inside and outside of the billet tend to be uniform.

[0022] Before the billet leaves the furnace, an infrared thermometer is used to check the surface temperature of the end and middle of the billet. If the temperature difference between the end and the middle is ≤30℃, the billet can be removed from the furnace and transferred to the forging station by a robot. If the temperature difference is >30℃, the billet is kept warm for 5 to 10 minutes and then re-inspected.

[0023] Preferably, the multi-dimensional parameter acquisition is performed by the online inspection station, specifically including the following steps:

[0024] The first step is to collect environmental parameters. The ambient temperature and relative humidity of the central area of ​​the testing station are collected by a temperature and humidity meter, and the convective wind speed at a height of 100mm above the testing station is collected by a hot-wire anemometer. The wind speed is collected for ≥5s and the stable value is taken.

[0025] The second step is surface temperature acquisition. Infrared thermometers are used to collect surface temperature at three locations: the blank tread surface, the nut mounting surface, and the inner wall of the pin hole. The time difference between the final forging demolding time and the temperature measurement completion time is recorded by the production line control system as the dwell time after final forging.

[0026] The third step is to determine the core temperature. This involves retrieving the final forging temperature, dwell time, and environmental heat dissipation conditions of a test block made of the same material and using the same forging process, and comparing it with the core surface temperature difference. Based on the measured surface temperature, dwell time after final forging, and environmental heat dissipation conditions, the corresponding core surface temperature difference is obtained. The surface temperature and the core surface temperature difference are then added together to obtain the core temperature.

[0027] The fourth step is to determine the degree of surface residual stress accumulation. The table of the relationship between the temperature drop process and the degree of surface residual stress accumulation under different final forging temperatures, different dwell times, and different environmental heat dissipation conditions, which was determined by the blind hole method after the test blocks of the same material and the same forging process were cooled to room temperature, was retrieved. Based on the measured temperature drop process, the level of surface residual stress accumulation was determined. The degree of surface residual stress accumulation is divided into three levels: low, medium, and high.

[0028] The fifth step is data binding, which involves binding and storing the surface temperature, core temperature, dwell time after final forging, ambient temperature, relative humidity, convection wind speed, and the level of surface residual stress accumulation with the blank batch number to the existing production line control system.

[0029] Preferably, the residual heat condition level in S4 is determined based on the higher of the core-surface temperature difference level and the surface residual stress accumulation level.

[0030] Preferably, the graded differentiated isothermal stress relief correction is performed by the heat preservation furnace and the transfer robot, specifically including the following steps:

[0031] Level identification: The transfer robot reads the waste heat condition data package bound to the blank, confirms the waste heat condition level to which the blank belongs, the input status is blank with level identifier, and the output status is blank to be released slowly.

[0032] Under the first-stage slow release and first-stage waste heat conditions, the billets are fed into a holding furnace with the furnace temperature set at 850℃~950℃ by a robotic arm. They are laid in a single layer with a billet spacing of ≥30mm and held for 20s~40s.

[0033] The billets are fed into a holding furnace with a furnace temperature set at 880℃~950℃ under the two-stage slow release and two-stage waste heat conditions. They are laid in a single layer with a billet spacing of ≥30mm and held for 40s~80s.

[0034] Three-stage slow release, three-stage waste heat working condition billet is sent into a holding furnace with furnace temperature set at 900℃~960℃, single layer flat with billet spacing ≥30mm, holding for 60s~120s.

[0035] After the furnace is removed from the furnace, the surface temperature of the key areas of the blank tread and nut mounting surface is detected by an infrared thermometer after the slow release is completed. The core surface temperature difference is determined by the initial core surface temperature difference level, heat preservation time, heat preservation temperature, measured surface temperature and core surface temperature difference after heat preservation, based on the test blocks of the same material and the same forging process and heat preservation slow release process. If the temperature difference is ≤30℃, it is transferred to the precision cutting station. If the temperature difference is >30℃, it is kept in heat for another 10 seconds and then re-inspected.

[0036] Preferably, the correspondence between the precision cutting process parameters and the waste heat condition level in S6 is as follows:

[0037] The first-level residual heat working condition corresponds to a precision cutting and stamping speed of 30mm / s to 50mm / s, a cutting feed rate of 2.0mm to 3.0mm, a die preheating compensation temperature of 150℃ to 200℃, and a holding time of 3s to 5s.

[0038] The secondary residual heat working condition corresponds to a precision cutting and punching speed of 20mm / s~30mm / s, a cutting feed rate of 1.5mm~2.5mm, a mold preheating compensation temperature of 200℃~250℃, and a holding pressure time of 5s~7s;

[0039] The three-level residual heat working condition corresponds to a precision cutting and stamping speed of 10mm / s to 20mm / s, a cutting feed rate of 1.0mm to 2.0mm, a mold preheating compensation temperature of 250℃ to 300℃, and a holding pressure duration of 6s to 8s.

[0040] Preferably, the S7 integrated forged hot-cut near-net-shape body includes the following steps:

[0041] For loading and positioning, the robot arm places the homogeneous and stable blank into the positioning cavity of the precision cutting die, with the blank tread surface facing up and the nut mounting surface facing down. The positioning pin is inserted into the process hole of the blank to achieve circumferential positioning. After positioning, the offset of the blank in each direction is ≤0.5mm.

[0042] Flash removal: As the press slide moves downward, the flash removal punch first contacts the outer edge of the blank and removes the flash at a matching precision punching speed. The removed flash is then discharged from below the die.

[0043] For tread surface finishing, the slide continues to descend 2mm to 5mm, and the tread surface finishing punch contacts the blank tread surface. The hot finishing of the tread surface is completed with a matching cutting feed rate. The cutting feed rate for tread surface finishing is determined according to the residual heat condition level.

[0044] The nut mounting surface is shaped, and the slider continues to descend to the bottom dead center. The nut mounting surface shaping punch contacts the nut mounting surface to complete the hot shaping. The pressure is held for 3 to 8 seconds. The input state is the tread forming blank.

[0045] After the mold is opened and the material is discharged, the slide returns to the top dead center, the ejector rod pushes the blank out of the mold cavity, the robot arm holds the blank and transfers it to the residual heat treatment station.

[0046] Preferably, the specific steps of the waste heat treatment in S8 are as follows:

[0047] After precision cutting, the blank is immediately quenched in water when the temperature is between 800℃ and 900℃. The quenching medium is a polymer aqueous solution with a mass fraction of 5% to 10%. After quenching, it is immediately placed in a tempering furnace at 180℃ to 250℃ for tempering. The tempering holding time is ≥120min.

[0048] Preferably, when the forging production line resumes production after a shutdown of 10 to 30 minutes, the production line control system executes the resumption process according to the following steps:

[0049] The first step is to record the shutdown status. When the production line stops, record the shutdown time, the heating furnace holding temperature, the precision cutting die temperature, and the final forging temperature of the last blank before shutdown. The input status is the shutdown signal, and the output status is the shutdown status record data.

[0050] The second step is to preheat the production line before resuming production. 30 minutes before resuming production, the heating furnace is started and the temperature is raised to 1180℃~1220℃. The precision cutting mold is preheated to 250℃~350℃ by electric heating rods. The input status is the production line resumption command and the output status is the production line preheating completed.

[0051] The third step is the final forging of the first piece. The final forging temperature of the first piece of billet after resumption of production is controlled at 1100℃~1180℃. After the final forging, based on the temperature drop characteristics of the first piece after resumption of production, that is, the core-surface temperature difference reaches level three or the surface residual stress accumulation reaches level three, it is directly judged as level three residual heat condition. The input state is the first piece of billet after resumption of production, and the output state is the billet under level three residual heat condition.

[0052] The fourth step is the first piece slow release. The first piece of blank is sent into a holding furnace with a furnace temperature of 900℃~960℃ and held for 60s~120s. The input state is blank under the third-level waste heat condition, and the output state is homogeneous first piece of blank.

[0053] The fifth step is the fine cutting of the first piece. The fine cutting process parameters corresponding to the three-level residual heat working condition are used to complete the removal of flash, fine cutting of tread surface and shaping of nut mounting surface. The fine cutting stamping speed is 10mm / s~20mm / s. The input state is a homogeneous first piece blank, and the output state is a finely cut first piece blank.

[0054] Step 6, First piece inspection. After the first piece is precision cut, perform residual heat treatment according to S8 and cool to room temperature. Use a coordinate measuring machine to measure the flatness of the tread surface and the parallelism of the nut mounting surface. If the flatness of the tread surface is ≤0.15mm and the parallelism of the nut mounting surface is ≤0.20mm, then resume normal graded production. The input status is the first piece finished after heat treatment, and the output status is the first piece that has passed inspection and is ready for re-production.

[0055] Preferably, when the ambient temperature in the workshop is ≤10℃ and the convective wind speed is ≥1m / s, the S3 parameter acquisition is completed within 30s after the final forging is completed, the preheating compensation temperature of the precision cutting die is increased by 30℃~50℃ based on the die preheating compensation temperature corresponding to the residual heat condition level of the blank, and the time for the blank to be transferred from the final forging station to the precision cutting station is ≤15s.

[0056] Preferably, when the blank is stacked and temporarily stored in the material frame for ≥60s, the material frame temporary storage station shall perform the following steps:

[0057] The first step is to temporarily store the blank in the frame. When the final forged blank cannot be precisely cut in time, the robot will put the blank into a heat-resistant steel material frame with a heat insulation pad at the bottom. The thickness of the heat insulation pad is ≥10mm. The input state is the final forged high temperature blank, and the output state is the blank temporarily stored in the frame.

[0058] The second step is to stack and arrange the blanks. The blanks are laid flat in a single layer with a spacing of ≥30mm. The number of stacked layers is ≤4. Heat-resistant steel spacers with a diameter of ≥8mm are placed between each layer. The input state is blanks entering the frame, and the output state is stacked temporary storage frames.

[0059] The third step is to temporarily store the time. The production line control system records the time and layer of each blank when it enters the frame. The input status is to temporarily store the blank, and the output status is to store the blank with the layer and duration records.

[0060] The fourth step is to determine the level of residual heat. After the temporary storage is completed, the residual heat condition level is determined based on the temperature drop characteristics corresponding to the stacking position. When the number of stacking layers is ≥3, the blanks in the middle layer that are covered by the blanks in the upper and lower layers are determined to be in a level 3 residual heat condition because the core-to-surface temperature difference reaches level 3 or the residual stress accumulation on the surface reaches level 3. The blanks in the uppermost and lowermost layers that are exposed to the air are determined to be in a level 2 residual heat condition. When the number of stacking layers is ≤2, all blanks are determined to be in a level 2 residual heat condition. The input status is blanks that have expired from temporary storage, and the output status is blanks with residual heat condition level markings.

[0061] The fifth step is slow-release precision cutting. The corresponding heat preservation slow-release process and precision cutting parameters are executed according to the determined residual heat condition level. The input status is blank with level label, and the output status is blank with precision cutting completed.

[0062] Preferably, the billet is 35MnB low-alloy structural steel, and its chemical composition by mass percentage is: C 0.32%~0.38%, Mn 1.10%~1.40%, Si 0.17%~0.37%, B 0.0005%~0.003%, Cr≤0.30%, P≤0.035%, S≤0.035%, with the balance being Fe and unavoidable impurities.

[0063] Preferably, the pressure for holding the pressure is 80% to 100% of the precision cutting and stamping pressure, and the blank is transferred to the S8 residual heat treatment station after the mold is opened and the natural cooling time in the air is ≤10s.

[0064] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0065] 1. This invention acquires the blank temperature field, dwell time and environmental heat dissipation conditions through multi-dimensional waste heat condition acquisition. After determining the waste heat condition level by dual-factor classification of core-surface temperature difference and residual stress, a differentiated constant temperature slow release process is matched according to the level to reduce the core-surface temperature difference and release the pre-existing residual stress. Then, the precision cutting speed, feed rate, mold temperature and holding time are dynamically matched so that each blank can be precision cut in an integrated manner under conditions that match its hot plasticity.

[0066] 2. Specialized treatments were designed for three types of disturbance scenarios in the forging production line that are generally overlooked by existing technologies: When resuming production after a short-term shutdown, the first piece is treated under the most stringent working conditions and only resumed mass production after passing the actual test after complete heat treatment; in low temperature and high wind speed environments, compensation is made simultaneously from three dimensions: collection time, mold preheating temperature, and transfer time; when blanks are stacked and temporarily stored, the working condition level is determined according to the heat dissipation difference between the middle layer and the upper and lower layers, and the slow release parameters are matched accordingly.

[0067] 3. The residual heat from forging is repositioned from waste heat that needs to be cooled and dissipated into a process resource that can be precisely utilized. Hot precision cutting is performed directly on the blank before it cools down to the critical phase transformation temperature, eliminating the need for air cooling to room temperature after forging and then milling the key working surfaces, thus reducing cutting allowance and tool consumption. After precision cutting, the residual heat of the blank, which is still in the appropriate quenching range, is used to directly quench it in water, eliminating the complete heating energy consumption of reheating and quenching after cooling.

[0068] 4. This solution uses the existing press in conjunction with the precision cutting die. The three actions of flash removal, tread precision cutting, and nut mounting surface shaping are completed sequentially and in staggered manner within one slide stroke of the press, eliminating the need to purchase precision cutting equipment. The online inspection station and the holding furnace can be directly arranged between the final forging and precision cutting stations of the existing forging production line, and the robotic arm transfer is compatible with the existing production line control system.

[0069] 5. This scheme homogenizes the temperature field in the austenitic region through staged isothermal slow release and releases the surface residual stress accumulated during the final forging and temporary storage process. It uses residual heat to quench with polymer aqueous solution to obtain a uniform martensitic structure, and then immediately tempers at low temperature to eliminate quenching brittleness and secondary shear stress generated by hot precision cutting. Attached Figure Description

[0070] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or components are generally identified by similar reference numerals. In the drawings, the elements or components are not necessarily drawn to scale.

[0071] Figure 1 This is a process flow diagram of the forging and hot precision cutting forming method of the present invention. Detailed Implementation

[0072] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore merely examples and should not be used to limit the scope of protection of the present invention. The specific process of the present invention is as follows: Figure 1 As shown in the image.

[0073] To make the technical solution of the present invention clearer, the present invention will now be further described: a method for hot-cutting and forming of dry track link for engineering machinery, characterized by comprising the following steps:

[0074] S1. Gradient heating and homogenization treatment of billet: The track link billet is heated in segments to the target forging temperature zone to reduce the plasticity difference caused by the initial band segregation of the billet and ensure that the metallographic structure and thermal expansion state of the billet are uniform and consistent before forging.

[0075] S2. Continuous die forging near net forming: The heated billet is pre-forged and shaped and then forged and filled in sequence to obtain a dry track link blank with a complete outline and retaining the high temperature residual heat of forging.

[0076] S3. Multi-dimensional waste heat condition parameter acquisition: Immediately after the final forging is completed, the billet temperature, the dwell time after final forging, the workshop ambient temperature and humidity, and the convection wind speed are acquired to obtain the original temperature field data of the billet caused by production intervals, ambient cooling, and stacking heat dissipation disturbances.

[0077] S4. Determination and Classification of Waste Heat Temperature Field: Based on the acquired parameters and the pre-calibrated temperature drop history and the correspondence with the surface residual stress, the real-time waste heat temperature field distribution of the blank is determined, the core-surface temperature difference gradient and the degree of surface residual stress accumulation are determined, and the blank is classified into different waste heat condition levels based on the comprehensive determination results of the core-surface temperature difference gradient and the degree of surface residual stress accumulation.

[0078] S5. Graded Differentiated Constant Temperature Stress Relief Correction: For blanks with different residual heat conditions, a homogeneous heat preservation and relief process with corresponding duration and temperature threshold is matched to reduce the core-surface temperature difference caused by non-uniform temperature drop, release the residual stress accumulated in the front surface layer during turnover and temporary storage, and make the overall temperature field and stress field of the blank tend to be homogeneous and stable.

[0079] S6. Adaptive Precision Cutting Parameter Dynamic Matching: Based on the residual heat condition level determined in S4, dynamically retrieve the precision cutting stamping speed, cutting feed, mold preheating compensation temperature and holding time that match the level to avoid forming deviation caused by the difference in metal springback under different residual heat conditions.

[0080] S7. Integrated forging, hot cutting, and near-net-shape forming: Before the blank temperature drops below the critical phase transformation temperature and within the high-temperature plastic steady state range, matching dynamic process parameters are used to simultaneously complete flash removal, tread surface cutting, and hot shaping of the nut mounting surface in one go, so as to achieve near-net-shape forming of key installation working surfaces.

[0081] S8. Residual heat window locking quenching and tempering: The residual heat temperature window of the blank is locked instantly after the precision cutting is completed, and the residual heat treatment process is immediately entered. This reduces the secondary shear stress generated by hot cutting, suppresses the latent deformation in the later stage, and achieves batch consistency of the forming accuracy, metallographic structure and mechanical properties of the track link under different disturbance conditions.

[0082] Specifically, this solution repositions forging waste heat from waste heat that needs to be cooled and dissipated into a process resource that can be precisely utilized; it ensures that the billet is always in a relatively controlled thermal state from heating to final heat treatment, and the output state of each step directly serves as the input condition for the next step, eliminating the energy waste and repeated structural transformations caused by intermediate cooling and reheating.

[0083] Unlike existing technologies that rely solely on operator visual observation of blank color or single-point temperature measurement to determine temperature status, this solution simultaneously collects blank temperature, dwell time, ambient temperature and humidity, and convection wind speed to comprehensively characterize the actual residual heat state of the blank after disturbances such as production interruptions, ambient cooling, and stacking heat dissipation. Furthermore, this solution incorporates temperature field unevenness and stress accumulation into the grading judgment, making the working condition level closer to the actual needs of precision cutting. Based on the working condition level, this solution dynamically adjusts four parameters: precision cutting speed, feed rate, mold temperature, and holding time, ensuring that the corresponding blank can be precision cut under conditions matching its thermoplasticity.

[0084] It needs to be clearly defined that the phase transformation critical temperature in S7 is approximately 780℃ to 800℃. Precision cutting must be carried out above the phase transformation critical temperature to ensure that the metal is in the austenitic single-phase region and has sufficient plasticity. The residual heat temperature window in S8 refers to the suitable quenching range of 800℃ to 900℃ when the blank temperature is still within the range after precision cutting. At this time, the blank has not been air-cooled and can be directly quenched in water.

[0085] Preferably, the gradient heating and homogenization treatment of the billet is performed by a walking beam furnace, specifically including the following steps:

[0086] The first step is furnace loading and arrangement. The operator lays the sawn bar billets of a fixed length in a single layer on the feeding platform. The spacing between the billets is ≥20mm. The length direction of the billets is perpendicular to the movement direction of the walking beam in the furnace. The arranged billets are sent to the heat-resistant steel fixed beam in the preheating section of the walking beam furnace. The input state is room temperature billets, and the output state is billets to be heated after furnace loading.

[0087] The second step is preheating. By controlling the stepping cycle of the walking beam, the average heating rate of the billet in the preheating section is ≤150℃ / h. The billet is heated from room temperature to 850℃~950℃ and held in this temperature range for 20min~40min, so that the temperature difference of the billet cross section is ≤50℃. The input state is room temperature billet, and the output state is billet that has been preheated and has a cross section temperature difference of ≤50℃.

[0088] The third step is homogenization and heating. The billet is gradually moved to the heating section by the walking beam inside the furnace chamber of the walking beam. By controlling the walking beam's walking cycle, the average heating rate of the billet in the heating section is ≤250℃ / h. It continues to rise to 1180℃~1220℃ and is held in this forging temperature range for 15min~30min to make the internal and external temperatures of the billet tend to be consistent. The input state is preheated billet, and the output state is high-temperature billet with uniform forging temperature.

[0089] The fourth step is furnace exit verification. Before the billet leaves the furnace, the surface temperature of the end and middle of the billet is checked by an infrared thermometer. The billet can be removed from the furnace if the temperature difference between the end and the middle is ≤30℃ and then transferred to the forging station by a robot. If the temperature difference is >30℃, it is kept at the temperature for another 5 to 10 minutes and then re-inspected. The input state is high temperature billet, and the output state is forging billet with uniform and qualified temperature.

[0090] Specifically, the four-step gradient heating process of the walking beam furnace in this solution eliminates the impact of initial material defects on the subsequent forging and hot cutting accuracy before the billet enters the forging process. Track link billets are typically sawn from continuously cast bars. Continuously cast billets inevitably contain banded segregation of elements such as carbon and manganese. This segregation leads to differences in plasticity and thermal expansion coefficients at different locations in the billet. If directly and rapidly heated to the forging temperature, the deformation resistance of the segregated areas differs from that of the matrix area, resulting in uneven microstructure and dimensional fluctuations after forging.

[0091] This scheme achieves gradual diffusion of alloying elements and temperature homogenization of the billet through segmented heating in the preheating and heating sections and cyclic control by a walking beam. Furthermore, it achieves a slow heating rate of ≤150℃ / h in the preheating section to avoid excessive temperature differences between the inside and outside of thick-section billets, thus preventing thermal stress. Existing technologies often employ rapid heating to increase production, resulting in a high surface temperature while the core remains at a low temperature. This large temperature difference generates thermal stress and can even lead to surface cracking. This scheme strictly controls the heating rate in the preheating section to below 150℃ / h and holds the temperature between 850℃ and 950℃ for 20 to 40 minutes, reducing the temperature difference across the billet cross-section to within 50℃. This lays the foundation for uniform temperature during the subsequent rapid heating in the soaking section.

[0092] Meanwhile, continuous and uniform heating is achieved through the linkage between the walking beam's stepping cycle and the heating rate. In the walking beam furnace, the billet is periodically moved from the preheating section to the heating section by the walking beam. The stepping cycle determines the residence time of the billet in each temperature zone. This scheme indirectly controls the average heating rate by controlling the stepping cycle, ensuring that the billet is always in a state of motion and heating within the furnace, avoiding localized overheating or uneven heating caused by the billet being stationary. Each piece is inspected before exiting the furnace if the temperature difference between the end and middle is ≤30℃. If the difference exceeds this limit, it is held at temperature for another 5 to 10 minutes for re-inspection to ensure uniform temperature along the entire length of each billet before forging. It is important to clarify that the length direction of the billet is perpendicular to the direction of movement of the walking beam to ensure that the billet passes through different temperature zones within the furnace simultaneously along its entire length during transport, avoiding longitudinal temperature differences. A spacing of ≥20mm ensures sufficient space for heat radiation between billets, preventing mutual obstruction and uneven heating.

[0093] Preferably, the acquisition of multi-dimensional waste heat operating parameters is performed by an online monitoring station, specifically including the following steps:

[0094] The first step is to collect environmental parameters. The ambient temperature and relative humidity of the central area of ​​the detection station are collected by a temperature and humidity meter, and the convective wind speed at a height of 100mm above the detection station is collected by a hot-wire anemometer. The wind speed collection time is ≥5s and a stable value is taken. The input status is the ambient air of the workshop, and the output status is the ambient temperature, relative humidity and convective wind speed data.

[0095] The second step is surface temperature acquisition. Within 5 seconds after the final forging demolding, the blank is transferred to the online inspection station by a robotic arm. An infrared thermometer is used to collect the surface temperature at three locations: the tread surface of the blank, the nut mounting surface, and the inner wall of the pin hole. The temperature is collected three times at each location and the arithmetic mean is taken. The arithmetic mean of the three locations is then taken as the surface temperature of the blank. The production line control system records the time difference between the final forging demolding time and the temperature measurement completion time as the dwell time after final forging. The input status is the high temperature blank after final forging, and the output status is the blank carrying the surface temperature and dwell time data.

[0096] The third step is to determine the core temperature. This involves retrieving the final forging temperature, dwell time, and environmental heat dissipation conditions of a test block made of the same material and forged using the same process, and comparing it with the core surface temperature difference. Based on the measured surface temperature, dwell time after final forging, and environmental heat dissipation conditions, the corresponding core surface temperature difference is found. The core temperature is obtained by adding the surface temperature and the core surface temperature difference (the difference between the core temperature and the surface temperature). The input data includes the surface temperature, dwell time after final forging, and environmental parameters, and the output data is the core temperature data.

[0097] The fourth step is to determine the degree of surface residual stress accumulation. This involves retrieving a table showing the relationship between the temperature drop history and the degree of surface residual stress accumulation under different final forging temperatures, dwell times, and environmental heat dissipation conditions, determined by the blind hole method using test blocks of the same material and forging process, cooled to room temperature. Based on the measured temperature drop history, the degree of surface residual stress accumulation is determined. The degree of surface residual stress accumulation is divided into three levels: low, medium, and high. A maximum absolute value of surface residual stress ≤150MPa is considered low; a maximum absolute value greater than 150MPa and ≤300MPa is considered medium; and a maximum absolute value >300MPa is considered high. The input is the temperature drop history data, and the output is the degree of surface residual stress accumulation.

[0098] The fifth step is data binding. The surface temperature, core temperature, dwell time after final forging, ambient temperature, relative humidity, convection wind speed, and the degree of accumulation of residual stress on the surface are bound to the blank batch number and stored in the existing production line control system. The input status is various scattered data, and the output status is the bound blank residual heat condition data package.

[0099] Specifically, this solution addresses the engineering problem of the inability to comprehensively, accurately, and non-destructively obtain the residual heat parameters of hot billets. The temperature of the billet after final forging reaches thousands of degrees Celsius, and it is in a continuous flow state during production, making detailed temperature and stress field measurements impossible as with laboratory samples. This solution constructs a complete non-contact residual heat condition sensing method suitable for industrial production lines. Furthermore, it prioritizes environmental parameter acquisition before billet temperature measurement to ensure consistent table lookup input time. This solution places environmental parameter acquisition as the first step, completing stable acquisition of ambient temperature, humidity, and wind speed before the billet reaches the testing station, ensuring strict matching of environmental parameters with the temperature measurement time during subsequent table lookups.

[0100] Meanwhile, the core temperature is indirectly determined by using a reference table calibrated with test blocks of the same material in existing technologies, avoiding destructive contact measurement. This solution pre-calibrates a reference table for the core-surface temperature difference using test blocks of the same material under different final forging temperatures, dwell times, and environmental heat dissipation conditions. In actual production, only the surface temperature and dwell time need to be measured to look up the core-surface temperature difference in the table. Then, the core temperature is added to the surface temperature to obtain the core temperature within the allowable error range. The entire process is completely non-contact and does not damage the blank.

[0101] The residual stress of hot blanks can be indirectly assessed by using the correlation table between temperature drop history and residual stress calibrated by the blind hole method in existing technology. Residual stress can usually only be measured by the blind hole method or X-ray method after the workpiece has cooled to room temperature. It cannot be directly measured in hot blanks. This solution simulates various temperature drop histories in advance with test blocks and measures the residual stress by the blind hole method after cooling. Based on the data results, the correlation between temperature drop history and residual stress accumulation degree is directly established. In actual production, the residual stress level can be determined by referring to the table based on the measured temperature drop history, thus realizing the assessment of stress state under hot conditions.

[0102] It needs to be clearly defined that the surface temperature is the average of three measurements taken at three locations: the tread surface, the nut mounting surface, and the inner wall of the pin hole. This is because these three locations represent the main working surface and thin-walled area of ​​the blank, respectively, and the average can reflect the overall surface temperature level. The maximum absolute value refers to the maximum value among the three principal stress absolute values, which accurately characterizes the degree of harm caused by residual stress.

[0103] Preferably, the waste heat condition level in S4 is determined based on the higher of the core-surface temperature difference level and the surface residual stress accumulation level; wherein, a core-surface temperature difference ≤50℃ is temperature difference level one, a core-surface temperature difference greater than 50℃ and ≤100℃ is temperature difference level two, and a core-surface temperature difference >100℃ is temperature difference level three; a low surface residual stress accumulation level is stress level one, a medium surface residual stress accumulation level is stress level two, and a high surface residual stress accumulation level is stress level three; the higher of the temperature difference level and the stress level is taken as the waste heat condition level.

[0104] Specifically, the dual-factor, three-level residual heat condition classification rule in this scheme addresses the problem that a single temperature parameter cannot comprehensively characterize the risks of hot-state blank precision cutting. The forming quality of hot-state precision cutting is simultaneously affected by two independent factors: the uniformity of the temperature field and the level of residual stress on the surface. A large core-to-surface temperature difference indicates uneven plasticity between the inside and outside of the blank, leading to dimensional deviations due to different springback amounts during precision cutting. High residual stress on the surface means that the blank will undergo stress release deformation during subsequent cutting and cooling. This scheme classifies these two dimensions separately and takes the higher one as the comprehensive level to ensure coverage of the most unfavorable factors. Meanwhile, the temperature difference classification boundaries of 50℃ and 100℃ directly correspond to the precision cutting springback risk level. When the core-to-surface temperature difference is ≤50℃, the difference in plasticity between the inside and outside of the blank is small, and the precision cutting springback amount is within tolerance and requires no special compensation. When the temperature difference is between 50℃ and 100℃, the difference in springback between the inside and outside is significant, requiring adjustment of precision cutting parameters for compensation. When the temperature difference exceeds 100℃, the difference in plasticity between the inside and outside is severe, necessitating a slow release before precision cutting. The residual stress grading boundaries of 150MPa and 300MPa correspond to different risks of subsequent deformation. When the maximum absolute value of residual stress is ≤150MPa, the deformation caused by stress release during subsequent cooling and cutting is within a controllable range. When the residual stress is between 150MPa and 300MPa, it is necessary to reduce stress through heat preservation before precision cutting. When it exceeds 300MPa, even with heat preservation, the most conservative precision cutting parameters must be used. The three grades correspond to three different process response intensities. It needs to be clearly defined that the higher grade in terms of numerical value means that grade three is higher than grade two, and grade two is higher than grade one. For example, when the temperature difference is grade one and the stress is grade two, grade two stress is taken as the residual heat condition grade; when the temperature difference is grade two and the stress is grade three, grade three stress is taken.

[0105] Preferably, the graded differentiated isothermal stress relief correction is performed by the heat preservation furnace and the transfer robot, specifically including the following steps:

[0106] The first step is level identification. The transfer robot reads the waste heat condition data package bound to the blank to confirm the waste heat condition level of the blank. The input status is blank with level identification, and the output status is blank to be slowed down.

[0107] The second step is a first-level slow release. The first-level waste heat condition blank is sent into the holding furnace with the furnace temperature set at 850℃~950℃ by a robot arm. It is laid in a single layer with a blank spacing of ≥30mm and held for 20s~40s. The input state is a first-level waste heat condition blank, and the output state is a homogeneous blank with a core surface temperature difference of ≤30℃ between the tread surface and the nut mounting surface in the key area.

[0108] The third step is the secondary slow release. The blank under the secondary waste heat condition is sent into the holding furnace with the furnace temperature set at 880℃~950℃. It is laid in a single layer with a blank spacing of ≥30mm and held for 40s~80s. The input state is the blank under the secondary waste heat condition, and the output state is the homogeneous blank with a core surface temperature difference of ≤30℃ between the tread surface and the nut mounting surface in the key area.

[0109] The fourth step is three-stage slow release. The blanks under the three-stage waste heat condition are sent into a holding furnace with the furnace temperature set at 900℃~960℃. They are laid in a single layer with a spacing of ≥30mm and held for 60s~120s. The input state is blanks under the three-stage waste heat condition, and the output state is a homogeneous blank with a core surface temperature difference of ≤30℃ between the tread surface and the nut mounting surface in the key area.

[0110] The fifth step is to verify the furnace exit. After the slow release is completed, the surface temperature of the key areas of the blank tread surface and nut mounting surface is detected by an infrared thermometer. The core surface temperature difference is determined according to the initial core surface temperature difference level, heat preservation time, heat preservation temperature, measured surface temperature and core surface temperature difference after heat preservation, which are determined by a reference table based on test blocks of the same material and with the same forging process and heat preservation slow release process. If the temperature difference is ≤30℃, it is transferred to the precision cutting station. If the temperature difference is >30℃, it is kept in heat for another 10 seconds and then re-inspected. The input state is the blank after slow release, and the output state is the blank in a homogeneous and steady state of temperature field and stress field.

[0111] Specifically, the five-step graded constant-temperature stress relief process in this solution addresses the core-to-surface temperature difference caused by non-uniform temperature drop after final forging and the residual surface stress accumulated during temporary storage. After the blank is removed from the final forging die, the surface directly contacts the air and dissipates heat quickly, while the core heat transfer is slow, resulting in a significant core-to-surface temperature difference within a short period. This solution matches different holding temperatures and durations according to the residual heat condition level, ensuring that the blank reaches a homogeneous and stable temperature and stress field before precision cutting. Furthermore, it achieves a precise match between the relief intensity and the degree of residual heat disturbance: Level 1 uses low temperature and short duration, while Level 3 uses high temperature and long duration. Level 1 uses 850℃ to 950℃ for 20 to 40 seconds, Level 2 uses 880℃ to 950℃ for 40 to 80 seconds, and Level 3 uses 900℃ to 960℃ for 60 to 120 seconds. The more severe the disturbance, the higher the holding temperature and the longer the time, ensuring a precise correspondence between the relief intensity and the requirements.

[0112] Meanwhile, after the slow release, each piece is verified by checking the core surface temperature difference with a reference table to ensure it is ≤30℃. After the slow release is completed, the surface temperature of key areas is detected by an infrared thermometer. The core surface temperature difference after heat preservation is checked by a pre-calibrated reference table. Only pieces with a temperature difference ≤30℃ are allowed to be transferred for precision cutting. If the difference exceeds the limit, heat preservation is continued for 10 seconds before re-inspection to ensure that the slow release effect of each blank meets the standard.

[0113] A single-layer, flat-laying method with a billet spacing of ≥30mm avoids uneven heating caused by billets blocking each other. This requires single-layer flat-laying with a minimum spacing of 30mm to ensure that all six sides of each billet are in full contact with the hot air inside the furnace, resulting in a uniform temperature after heat preservation. It needs to be clearly defined that the slow-release temperature of 850℃ to 960℃ promotes uniform core surface temperature through heat conduction, while simultaneously releasing residual surface stress through high-temperature creep. The tread surface and nut mounting surface are critical areas referring to the two main working surfaces for subsequent precision cutting. The temperature difference between these two areas directly affects the precision cutting dimensional accuracy, and therefore they are key areas for verification.

[0114] Preferably, the correspondence between the precision cutting process parameters and the waste heat condition level in S6 is as follows:

[0115] The first-level residual heat working condition corresponds to a precision cutting and stamping speed of 30mm / s to 50mm / s, a cutting feed rate of 2.0mm to 3.0mm, a die preheating compensation temperature of 150℃ to 200℃, and a holding time of 3s to 5s.

[0116] The secondary residual heat working condition corresponds to a precision cutting and punching speed of 20mm / s~30mm / s, a cutting feed rate of 1.5mm~2.5mm, a mold preheating compensation temperature of 200℃~250℃, and a holding pressure time of 5s~7s;

[0117] The three-level residual heat working condition corresponds to a precision cutting and stamping speed of 10mm / s to 20mm / s, a cutting feed rate of 1.0mm to 2.0mm, a mold preheating compensation temperature of 250℃ to 300℃, and a holding pressure duration of 6s to 8s.

[0118] Specifically, this solution maps four key parameters to three operating conditions, achieving adaptive matching of parameters according to the operating conditions. The first-level operating condition uses a higher speed of 30mm / s to 50mm / s, at which the blank temperature is uniform and the plasticity is good. High-speed precision cutting can improve production efficiency and avoid tearing. The second-level operating condition reduces the speed to 20mm / s to 30mm / s, appropriately reducing the speed to adapt to the blank with decreased plasticity. The third-level operating condition further reduces the speed to 10mm / s to 20mm / s. Low-speed precision cutting gives the metal sufficient time for plastic flow and avoids surface micro-cracks in the low-temperature, high-stress blank under rapid shearing. Meanwhile, the mold preheating compensation temperature gradually increases with the working condition level. For Level 1, a mold temperature of 150℃ to 200℃ is sufficient because the blank itself is hot and the temperature drop upon contact with the mold is small. For Level 3, the mold temperature increases to 250℃ to 300℃ because the surface temperature of the low-temperature blank drops sharply upon contact with the cold mold, causing a rapid decrease in the plasticity of the surface metal. Increasing the mold temperature reduces the temperature difference between the blank and the mold, mitigating the temperature drop upon contact. Currently, the mold temperature is typically fixed at around 200℃ and is not adjusted according to the workpiece condition. The holding pressure duration gradually increases with the working condition level. For Level 1, 3 to 5 seconds of holding pressure is sufficient to shape the high-temperature blank; for Level 3, 6 to 8 seconds of holding pressure provides more sufficient time for plastic shaping and stress relaxation of the low-temperature, high-stress blank, reducing springback deformation after demolding. It needs to be clearly defined that the cutting feed rate is 2.0mm to 3.0mm for level 1, 1.5mm to 2.5mm for level 2, and 1.0mm to 2.0mm for level 3. The feed rate decreases as the level increases because the plasticity of the blank is poor at low temperatures, and a large feed rate will lead to excessive cutting force and a decrease in surface quality. The four parameters are adjusted simultaneously rather than individually because the effects of speed, feed rate, mold temperature, and holding time on springback are interactive and must be adjusted in a coordinated manner to achieve accurate springback compensation.

[0119] Preferably, the S7 integrated forging hot precision cutting near-net-shape forming is performed by an existing press in conjunction with a precision cutting die mounted on it, specifically including the following steps:

[0120] The first step is material loading and positioning. The robot arm puts the homogeneous and stable blank into the positioning cavity of the precision cutting mold, with the blank tread surface facing up and the nut mounting surface facing down. The positioning pin is inserted into the process hole of the blank to achieve circumferential positioning. After positioning, the offset of the blank in each direction is ≤0.5mm. The input state is the homogeneous and stable blank, and the output state is the blank to be precision cut after positioning.

[0121] The second step is to remove the flash. The press slide moves down and the cutting punch first contacts the flash on the outer edge of the blank. The flash is removed at a matching precision punching speed. The removed flash is discharged from under the mold. The input state is blank with flash and the output state is blank without flash.

[0122] The third step is the tread surface precision cutting. The slider continues to descend 2mm to 5mm, and the tread surface precision cutting punch contacts the blank tread surface. The hot tread surface precision cutting is completed with a matching cutting feed. The cutting feed of the tread surface precision cutting is determined according to the residual heat condition level. Level 1 residual heat condition is 2.0mm to 3.0mm, Level 2 is 1.5mm to 2.5mm, and Level 3 is 1.0mm to 2.0mm. The input state is to remove the flash blank, and the output state is to form the tread surface blank.

[0123] The fourth step is to shape the nut mounting surface. The slider continues to descend to the bottom dead center. The nut mounting surface shaping punch contacts the nut mounting surface to complete the hot shaping. The pressure is held for 3 to 8 seconds. The input state is the tread forming blank, and the output state is the near-net-shape forming blank.

[0124] Step 5: Mold opening and material ejection. The slider returns to the top dead center, and the ejector rod pushes the blank out of the mold cavity. The robot arm holds the blank and transfers it to the residual heat treatment station. The input state is near-net-shape blank, and the output state is precision-cut blank.

[0125] Specifically, this solution integrates three actions—flash removal, tread face precision cutting, and nut mounting surface shaping—into a single stroke of an existing punch press, ensuring the blank remains in a relatively controlled hot and positioned state from entry to exit. Furthermore, it achieves staggered sequential completion of these three cutting and shaping actions within the same press stroke. During the slide's descent, the flash removal punch contacts the flash first, followed by the tread face precision cutting punch after the slide continues 2mm to 5mm down. Finally, the nut mounting surface shaping punch completes the shaping. This staggered timing avoids the impact of peak forming forces on the press and die. Simultaneously, the tread face precision cutting feed rate dynamically adjusts according to the residual heat level: 2.0mm to 3.0mm for level one, 1.5mm to 2.5mm for level two, and 1.0mm to 2.0mm for level three. The cutting depth precisely matches the material's current plasticity. Existing technology has a fixed tread face cutting depth; excessive cutting depth in high-temperature blanks leads to overcutting, while insufficient cutting depth in low-temperature blanks results in excessive allowance requiring further processing. The locating pin is inserted into the process hole to achieve precise circumferential positioning with an offset of ≤0.5mm. The hot blank surface has oxide scale and an irregular shape; relying solely on the cavity contour for positioning can easily lead to circumferential deflection. This solution utilizes the existing process hole on the blank to insert the locating pin, restricting the blank's rotation and horizontal movement, achieving a positioning accuracy within 0.5mm, and ensuring the positional accuracy of the tread and nut surfaces relative to the pin hole. It needs to be clearly defined that the 2mm to 5mm downward movement of the slide block inside the press refers to the idle stroke from the point where the flash is removed to the point where the tread face punch contacts the blank. This distance is determined by the height difference between the trimming punch and the tread face punch, ensuring that the tread face is completely removed before precision cutting begins. The placement direction with the tread face upward and the nut mounting surface downward ensures that the tread face precision cutting is completed by the upper die punch, and the nut surface shaping is completed by the lower die cavity. The two working surfaces are formed by the upper and lower dies respectively without interference.

[0126] Preferably, the specific steps of the waste heat treatment in S8 are as follows:

[0127] After precision cutting, the blank is immediately quenched in water when the temperature is between 800℃ and 900℃. The quenching medium is a polymer aqueous solution with a mass fraction of 5% to 10%. After quenching, it is immediately placed in a tempering furnace at 180℃ to 250℃ for tempering. The tempering holding time is ≥120min.

[0128] Specifically, this solution utilizes the residual heat after precision cutting for direct quenching, followed by immediate tempering, seamlessly integrating forming and heat treatment. The residual heat of the pre-cut blank is used for direct water quenching in the 800℃ to 900℃ range, eliminating the need for reheating. While the blank temperature drops slightly due to heat dissipation from contact with the mold after precision cutting, it remains within the 800℃ to 900℃ austenitizing temperature range. This solution directly utilizes the residual heat for quenching, saving the energy consumption of a complete heating cycle for each product. Meanwhile, a polymer aqueous solution with a mass fraction of 5% to 10% is used as the quenching medium. The cooling rate is between that of water and oil. 35MnB steel contains boron, which has good hardenability. However, if water is used for quenching, the cooling rate is too fast, and quenching cracks are easily generated at areas with uneven thickness. If mineral oil is used for quenching, the cooling rate is insufficient, and thick sections cannot be fully hardened. The concentration of the polymer aqueous solution (such as polyalkylene glycol-based quenching fluid) can adjust the cooling characteristics. The cooling rate at a concentration of 5% to 10% can meet the hardenability requirements of 35MnB steel and avoid the risk of cracking. Immediately after quenching, the steel is placed in a tempering furnace at 180℃ to 250℃ and held for at least 120 minutes to promptly eliminate quenching stress and secondary shear stress from precision cutting. This method of directly entering the tempering furnace without waiting at room temperature after quenching eliminates brittleness and stress through low-temperature tempering when martensite is just forming. At the same time, the secondary shear stress generated by precision cutting is also eliminated during tempering. It needs to be clearly defined that 800℃ to 900℃ is higher than the Ac3 temperature of 35MnB steel, ensuring that the microstructure before quenching is fully austenitic; 180℃ to 250℃ is the low-temperature tempering temperature, which obtains tempered martensite microstructure after tempering, and the hardness is maintained in the range of HRC45 to 55 to meet the wear resistance requirements of the track links; the water immersion action should be completed within 10 seconds after the precision cutting and die opening to avoid air cooling exceeding the quenching window.

[0129] Preferably, when the forging production line resumes production after a shutdown of 10 to 30 minutes, the production line control system executes the resumption process according to the following steps:

[0130] The first step is to record the shutdown status. When the production line stops, record the shutdown time, the heating furnace holding temperature, the precision cutting die temperature, and the final forging temperature of the last blank before shutdown. The input status is the shutdown signal, and the output status is the shutdown status record data.

[0131] The second step is to preheat the production line before resuming production. 30 minutes before resuming production, the heating furnace is started and the temperature is raised to 1180℃~1220℃. The precision cutting mold is preheated to 250℃~350℃ by electric heating rods. The input status is the production line resumption command and the output status is the production line preheating completed.

[0132] The third step is the final forging of the first piece. The final forging temperature of the first piece of billet after resumption of production is controlled at 1100℃~1180℃. After the final forging, based on the temperature drop characteristics of the first piece after resumption of production, that is, the core-surface temperature difference reaches level three or the surface residual stress accumulation reaches level three, it is directly judged as level three residual heat condition. The input state is the first piece of billet after resumption of production, and the output state is the billet under level three residual heat condition.

[0133] The fourth step is the first piece slow release. The first piece of blank is sent into a holding furnace with a furnace temperature of 900℃~960℃ and held for 60s~120s. The input state is blank under the third-level waste heat condition, and the output state is homogeneous first piece of blank.

[0134] The fifth step is the fine cutting of the first piece. The fine cutting process parameters corresponding to the three-level residual heat working condition are used to complete the removal of flash, fine cutting of tread surface and shaping of nut mounting surface. The fine cutting stamping speed is 10mm / s~20mm / s. The input state is a homogeneous first piece blank, and the output state is a finely cut first piece blank.

[0135] Step 6, First piece inspection. After the first piece is precision cut, perform residual heat treatment according to S8 and cool to room temperature. Use a coordinate measuring machine to measure the flatness of the tread surface and the parallelism of the nut mounting surface. If the flatness of the tread surface is ≤0.15mm and the parallelism of the nut mounting surface is ≤0.20mm, then resume normal graded production. The input status is the first piece finished after heat treatment, and the output status is the first piece that has passed inspection and is ready for re-production.

[0136] Specifically, this solution targets short-to-medium-duration downtime scenarios of 10 to 30 minutes. It designs a complete resumption process from downtime recording to first-piece inspection, enabling the first piece to be directly identified as a Level III residual heat condition and employing the most stringent slow-release and precision cutting parameters. During resumption, the mold temperature is low, the blank temperature drops rapidly after final forging, and the core-surface temperature difference and residual stress are at a high level. This solution bypasses the normal parameter acquisition and grading process and directly treats it as a Level III condition, using the strongest slow release at 900℃ to 960℃ for 60s to 120s and the lowest precision cutting speed of 10mm / s to 20mm / s to ensure the quality of the first piece in the most conservative way. Existing technologies often treat the first piece of the resumed production as a normal Level I or Level II condition, with overly aggressive parameters leading to tearing or deformation of the first piece.

[0137] Simultaneously, 30 minutes before resuming production, the heating furnace and die electric heating are started to preheat the furnace to the normal forging temperature of 1180℃ to 1220℃, and the precision cutting die is preheated to 250℃ to 350℃ using electric heating rods. This ensures that the equipment is in normal production condition before resuming production, avoiding excessively rapid temperature drop of the blank caused by the cold die absorbing heat. After the first piece undergoes complete heat treatment, its flatness and parallelism are measured using a coordinate measuring machine. Only after passing the test can normal graded production resume. The first piece after resuming production must undergo quenching, tempering, and cooling to room temperature before dimensional inspection. The flatness of the tread surface must be ≤0.15mm and the parallelism of the nut mounting surface must be ≤0.20mm before subsequent products are allowed to be produced according to the normal graded process. If the first piece fails to meet the requirements, the equipment condition needs to be checked and trial production needs to be restarted. This establishes a verification checkpoint for the quality of resuming production. With existing technology, mass production is carried out directly during resuming production, and by the time defects are discovered, a large number of scraps have already been generated. It needs to be clearly defined that the downtime is limited to 10 to 30 minutes. If the downtime is less than 10 minutes and the equipment temperature has not dropped significantly, no special restart procedure is required. If the downtime exceeds 30 minutes and the equipment has cooled down completely, the cold start procedure should be followed. The final forging temperature of the first piece should be controlled at 1100℃ to 1180℃, slightly lower than the normal furnace exit temperature of 1180℃ to 1220℃, which corresponds to the final forging temperature. This is because cold dies absorb heat quickly, and the final forging temperature needs to be appropriately increased to ensure that there is still sufficient plasticity during the final forging.

[0138] Preferably, when the ambient temperature in the workshop is ≤10℃ and the convective wind speed is ≥1m / s, the S3 parameter acquisition is completed within 30s after the final forging is completed, the preheating compensation temperature of the precision cutting die is increased by 30℃~50℃ based on the die preheating compensation temperature corresponding to the residual heat condition level of the blank, and the time for the blank to be transferred from the final forging station to the precision cutting station is ≤15s.

[0139] Specifically, this solution compensates for all parameters within 30 seconds after final forging under low temperature and high wind speed conditions by simultaneously compensating for data acquisition time, mold temperature, and transfer time. Normally, parameter acquisition might take longer, but under these conditions, every extra second the blank remains exposed results in heat loss. This solution compresses the acquisition time to within 30 seconds, including environmental parameter pre-acquisition, blank transfer, three-point temperature measurement, and table lookup calculations, ensuring that the acquired parameters reflect the true state of the blank immediately after final forging, rather than its state after excessive cooling. Simultaneously, the mold preheating compensation temperature is increased by 30°C to 50°C from the corresponding level. In low-temperature environments, the mold temperature itself is also low, and the temperature drop after the blank contacts the mold is greater than in a normal temperature environment. Increasing the mold temperature reduces the temperature difference between the blank and the mold, slowing down the contact temperature drop and ensuring that the tread and nut surfaces remain within the plastic temperature range during the precision cutting process. Existing technology maintains a fixed mold temperature year-round, and in winter, the lower mold temperature causes rapid cooling of the blank surface upon contact. The transfer time from the final forging station to the precision cutting station should be ≤15s. The transfer path and speed of the robotic arm need to be optimized in low-temperature environments to minimize the exposure time of the blank in cold air. Completing the transfer within 15s means that the temperature drop of the blank is controlled within an acceptable range throughout the entire process from final forging demolding to entering the precision cutting die. It needs to be clearly defined that the triggering condition for this compensation process is that the ambient temperature ≤10℃ and the convective wind speed ≥1m / s must be met simultaneously. If there is only low temperature but very low wind speed, the temperature drop is not serious. If there is only wind speed but the ambient temperature is not low, the temperature drop is also within a controllable range. Compensation is triggered only when both conditions are met simultaneously. The increase in die temperature by 30℃ to 50℃ is based on the die temperature of the corresponding weight 6 level. For example, the original die temperature of level 1 is 150℃ to 200℃, and after compensation it is 180℃ to 250℃.

[0140] Preferably, when the blank is stacked and temporarily stored in the material frame for ≥60s, the material frame temporary storage station shall perform the following steps:

[0141] The first step is to temporarily store the blank in the frame. When the final forged blank cannot be precisely cut in time, the robot will put the blank into a heat-resistant steel material frame with a heat insulation pad at the bottom. The thickness of the heat insulation pad is ≥10mm. The input state is the final forged high temperature blank, and the output state is the blank temporarily stored in the frame.

[0142] The second step is to stack and arrange the blanks. The blanks are laid flat in a single layer with a spacing of ≥30mm. The number of stacked layers is ≤4. Heat-resistant steel spacers with a diameter of ≥8mm are placed between each layer. The input state is blanks entering the frame, and the output state is stacked temporary storage frames.

[0143] The third step is to temporarily store the time. The production line control system records the time and layer of each blank when it enters the frame. The input status is to temporarily store the blank, and the output status is to store the blank with the layer and duration records.

[0144] The fourth step is to determine the level of residual heat. After the temporary storage is completed, the residual heat condition level is determined based on the temperature drop characteristics corresponding to the stacking position. When the number of stacking layers is ≥3, the blanks in the middle layer that are covered by the blanks in the upper and lower layers are determined to be in a level 3 residual heat condition because the core-to-surface temperature difference reaches level 3 or the residual stress accumulation on the surface reaches level 3. The blanks in the uppermost and lowermost layers that are exposed to the air are determined to be in a level 2 residual heat condition. When the number of stacking layers is ≤2, all blanks are determined to be in a level 2 residual heat condition. The input status is blanks that have expired from temporary storage, and the output status is blanks with residual heat condition level markings.

[0145] The fifth step is slow-release precision cutting. The corresponding heat preservation slow-release process and precision cutting parameters are executed according to the determined residual heat condition level. The input status is blank with level label, and the output status is blank with precision cutting completed.

[0146] Specifically, this solution addresses scenarios with a storage time ≥60s and designs a complete processing flow from frame entry to grade determination. It determines different residual heat levels based on stacking layer differences: Level 3 for the middle layer and Level 2 for the top and bottom layers. The solution also determines the grade based on the heat dissipation characteristics of each layer, treating the middle layer as Level 3 and the top and bottom layers as Level 2. Simultaneously, a heat insulation pad with a thickness ≥10mm is installed at the bottom of the frame to reduce bottom heat conduction. The thermal conductivity of the heat-resistant steel frame is much greater than that of air. If the blank is placed directly at the bottom of the frame, the lower surface will rapidly dissipate heat through the metal, causing a sharp drop in the temperature of the bottommost blank surface. The heat insulation pad, made of refractory fiber or ceramic material with low thermal conductivity, effectively blocks heat conduction between the blank and the frame. Heat-resistant steel spacers with a diameter of ≥8mm are placed between each layer to form air gaps. These spacers separate the upper and lower layers of blanks, creating an air circulation layer in between. This not only supports the weight of the stack but also prevents the blanks from sticking together and causing localized temperature drops due to direct contact. The presence of air gaps allows the upper and lower surfaces of each layer of blanks to contact the air for heat dissipation, resulting in much more uniform heat dissipation than direct stacking. It is important to clarify that stacking ≤4 layers is to control the total height to prevent the lower blanks from being deformed by the weight of the upper layers, while ensuring the stability of the spacer support. This process is only triggered when the storage time is ≥60s, because the temperature drop of blanks stored for less than 60s is not significant and can be handled according to the normal process. The middle layer refers to the layers other than the top and bottom layers when stacking ≥3 layers. For example, when stacking 3 layers, the middle layer is the 2nd layer; when stacking 4 layers, the middle layers are the 2nd and 3rd layers.

[0147] Preferably, the billet is 35MnB low-alloy structural steel, and its chemical composition by mass percentage is: C 0.32%~0.38%, Mn 1.10%~1.40%, Si 0.17%~0.37%, B 0.0005%~0.003%, Cr≤0.30%, P≤0.035%, S≤0.035%, with the balance being Fe and unavoidable impurities.

[0148] Specifically, 35MnB steel is a commonly used material for engineering machinery track links. This solution precisely defines the composition range to improve its compatibility with forging and hot cutting processes. Furthermore, a boron content of 0.0005% to 0.003% (i.e., 5ppm to 30ppm) significantly improves hardenability. Boron is one of the most effective elements for improving steel hardenability; even trace amounts of boron can significantly enhance hardenability, allowing for the formation of a fully martensitic structure even when using a slow-cooling polymer aqueous solution during residual heat quenching. This solution utilizes the microalloying effect of boron to improve hardenability without increasing alloy costs.

[0149] Meanwhile, a manganese content of 1.10% to 1.40% synergistically enhances hardenability with boron while maintaining good hot plasticity. Manganese is an austenite stabilizing element; its solid solution in austenite lowers the phase transformation temperature and improves hardenability. Simultaneously, the solid solution strengthening effect of manganese does not significantly reduce high-temperature plasticity. The synergistic effect of 1.10% to 1.40% manganese content and boron ensures that 35MnB steel retains good hot plasticity at 800℃ to 900℃, making it suitable for hot precision cutting of tread and nut surfaces, unlike high-chromium or high-nickel alloy steels which exhibit high deformation resistance and poor hot plasticity at high temperatures. This scheme controls phosphorus and sulfur to below 0.035% to ensure grain boundary strength during hot precision cutting and reduce the tendency for surface microcracks on tread and nut surfaces.

[0150] Preferably, the pressure for holding the pressure is 80% to 100% of the precision cutting and stamping pressure, and the blank is transferred to the S8 residual heat treatment station after the mold is opened and the natural cooling time in the air is ≤10s.

[0151] Specifically, the final step in precision cutting is pressure holding. The purpose of pressure holding is to ensure the hot metal fully fills the mold cavity, completes recrystallization, and stabilizes its dimensions. If the pressure holding is insufficient, the metal cannot fully conform to the mold cavity, resulting in significant springback after demolding. Conversely, if the pressure holding is sufficient but the air-cooling time after mold opening is too long, the blank temperature drops below 800℃, exceeding the residual heat quenching window, making direct residual heat quenching impossible. This solution links the pressure holding and air-cooling time parameters to ensure that both the forming and residual heat quenching stages meet the requirements. This solution increases the pressure holding to 80% to 100%, approaching the full pressure during precision cutting, allowing the metal to fully fill the cavity and achieve dimensional stability under high pressure. Meanwhile, after mold opening, the air cooling time is ≤10s before transferring to the residual heat treatment station. The temperature drop from precision cutting to quenching is strictly controlled. When precision cutting is completed, the blank temperature is about 850℃ to 950℃. After mold opening, the temperature drops by about 5℃ to 10℃ per second in the air. If the air cooling exceeds 10s, the blank temperature may drop below 800℃, which is lower than the Ac3 temperature of 35MnB steel. At this time, water quenching cannot obtain a complete martensitic structure. This solution requires that the transfer from the mold to the quenching tank be completed within 10s after mold opening to ensure that the water quenching temperature is within the window of 800℃ to 900℃.

[0152] During the holding pressure stage, 80% to 100% high pressure is applied to fully shape the tread and nut surfaces. A rapid transfer of ≤10 seconds after mold opening ensures the blank remains within the quenching temperature window. Two parameters, one controlling the precision cutting quality and the other controlling the heat treatment conditions, work together to ensure a continuous transition from precision cutting to residual heat quenching. It is important to clearly define that the precision cutting stamping pressure refers to the total forming force applied by the press slide during tread precision cutting and nut surface shaping. The holding pressure is 80% to 100% of this force, maintained by the press's hydraulic system at the bottom dead center. The natural cooling time in air refers to the time from the slide's return stroke and mold opening, when the blank leaves the mold cavity, until the blank is immersed below the surface of the quenching medium, including the total time for robotic gripping, transfer, and water immersion.

[0153] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. For those skilled in the art, any alternative improvements or transformations made to the implementation of the present invention fall within the protection scope of the present invention.

[0154] Any aspects of this invention not described in detail are well-known to those skilled in the art.

Claims

1. A method for hot-cutting and forming of dry track link sections for engineering machinery, characterized in that, Includes the following steps: S1. Gradient heating homogenization treatment of billet; S2. The heated billet is pre-forged and shaped, and then forged and filled to obtain a dry track link blank with a complete outline and retaining the high temperature residual heat of forging. S3. Immediately after the final forging is completed, acquire multiple parameters such as billet temperature, dwell time after final forging, workshop ambient temperature and humidity, and convection wind speed to obtain the original temperature field data of the billet caused by production intervals, ambient cooling, and stacking heat dissipation disturbances. S4. Based on the acquired parameters and the pre-calibrated temperature drop history and the corresponding relationship with the surface residual stress, determine the real-time waste heat temperature field distribution of the blank, determine the core-surface temperature difference gradient and the degree of surface residual stress accumulation, and then classify the blank into different waste heat working condition levels. S5. For blanks with different waste heat conditions, a homogeneous heat preservation and slow release process with corresponding duration and temperature threshold is matched to make the overall temperature field and stress field of the blank tend to be homogeneous and stable. S6, Dynamic matching of precision cutting parameters for adaptive working conditions: Based on the residual heat working condition level determined in S4, dynamically retrieve the precision cutting stamping speed, cutting feed, mold preheating compensation temperature and holding time that match the level. S7. Before the blank temperature drops below the critical temperature for phase transformation and within the range of high-temperature plastic stability, use the matched dynamic process parameters to simultaneously complete the flash removal, tread precision cutting, and hot shaping of the nut mounting surface in one go. S8. After the precision cutting is completed, the residual heat temperature window of the blank is locked instantly, and the residual heat treatment process is immediately started to achieve batch consistency of the forming accuracy, metallographic structure and mechanical properties of the track link under different disturbance conditions.

2. The method according to claim 1, characterized in that, in, The gradient heating and homogenization process of the billet is performed by a walking beam furnace, specifically including the following steps: For furnace loading and arrangement, the operator lays the sawn bar billets of fixed length in a single layer on the feeding platform, with a spacing of ≥20mm between billets. The length direction of the billets is perpendicular to the movement direction of the walking beam in the furnace. The arranged billets are then fed onto the heat-resistant steel fixed beam in the preheating section of the walking beam furnace. Preheating is carried out by controlling the stepping cycle of the walking beam to ensure that the average heating rate of the billet in the preheating section is ≤150℃ / h, heating the billet from room temperature to 850℃~950℃, and holding it in this temperature range for 20min~40min to ensure that the temperature difference of the billet cross section is ≤50℃. The billet is gradually moved to the heating section by the walking beam inside the furnace chamber of the walking beam heating furnace. By controlling the walking beam's walking cycle, the average heating rate of the billet in the heating section is ≤250℃ / h. It continues to rise to 1180℃~1220℃ and is held in this forging temperature range for 15min~30min to make the temperature inside and outside of the billet tend to be uniform. Before the billet leaves the furnace, an infrared thermometer is used to check the surface temperature of the end and middle of the billet. If the temperature difference between the end and the middle is ≤30℃, the billet can be removed from the furnace and transferred to the forging station by a robot. If the temperature difference is >30℃, the billet is kept warm for 5 to 10 minutes and then re-inspected.

3. The method according to claim 1, characterized in that, Multi-dimensional parameter acquisition is performed by the online inspection station, specifically including the following steps: The first step is to collect environmental parameters. The ambient temperature and relative humidity of the central area of ​​the testing station are collected by a temperature and humidity meter, and the convective wind speed at a height of 100mm above the testing station is collected by a hot-wire anemometer. The wind speed is collected for ≥5s and the stable value is taken. The second step is surface temperature acquisition. Infrared thermometers are used to collect surface temperature at three locations: the blank tread surface, the nut mounting surface, and the inner wall of the pin hole. The time difference between the final forging demolding time and the temperature measurement completion time is recorded by the production line control system as the dwell time after final forging. The third step is to determine the core temperature. This involves retrieving the final forging temperature, dwell time, and environmental heat dissipation conditions of a test block made of the same material and using the same forging process, and comparing it with the core surface temperature difference. Based on the measured surface temperature, dwell time after final forging, and environmental heat dissipation conditions, the corresponding core surface temperature difference is obtained. The surface temperature and the core surface temperature difference are then added together to obtain the core temperature. The fourth step is to determine the degree of surface residual stress accumulation. The table of the relationship between the temperature drop process and the degree of surface residual stress accumulation under different final forging temperatures, different dwell times, and different environmental heat dissipation conditions, which was determined by the blind hole method after the test blocks of the same material and the same forging process were cooled to room temperature, was retrieved. Based on the measured temperature drop process, the level of surface residual stress accumulation was determined. The degree of surface residual stress accumulation is divided into three levels: low, medium, and high. The fifth step is data binding, which involves binding and storing the surface temperature, core temperature, dwell time after final forging, ambient temperature, relative humidity, convection wind speed, and the level of surface residual stress accumulation with the blank batch number to the existing production line control system.

4. The method according to claim 1, characterized in that, The residual heat condition level in S4 is determined based on the higher of the core-surface temperature difference level and the surface residual stress accumulation level.

5. The method according to claim 4, characterized in that, The graded differentiated isothermal stress relief correction is performed by the holding furnace and the transfer robot, specifically including the following steps: Level identification: The transfer robot reads the waste heat condition data package bound to the blank, confirms the waste heat condition level to which the blank belongs, the input status is blank with level identifier, and the output status is blank to be released slowly. Under the first-stage slow release and first-stage waste heat conditions, the billets are fed into a holding furnace with the furnace temperature set at 850℃~950℃ by a robotic arm. They are laid in a single layer with a billet spacing of ≥30mm and held for 20s~40s. The billets are fed into a holding furnace with a furnace temperature set at 880℃~950℃ under the two-stage slow release and two-stage waste heat conditions. They are laid in a single layer with a billet spacing of ≥30mm and held for 40s~80s. Three-stage slow release, three-stage waste heat working condition billet is sent into a holding furnace with furnace temperature set at 900℃~960℃, single layer flat with billet spacing ≥30mm, holding for 60s~120s. After the furnace is removed from the furnace, the surface temperature of the key areas of the blank tread and nut mounting surface is detected by an infrared thermometer after the slow release is completed. The core surface temperature difference is determined by the initial core surface temperature difference level, heat preservation time, heat preservation temperature, measured surface temperature and core surface temperature difference after heat preservation, based on the test blocks of the same material and the same forging process and heat preservation slow release process. If the temperature difference is ≤30℃, it is transferred to the precision cutting station. If the temperature difference is >30℃, it is kept in heat for another 10 seconds and then re-inspected.

6. The method according to claim 4, characterized in that, The correspondence between the precision cutting process parameters and the residual heat condition level in S6 is as follows: The first-level residual heat working condition corresponds to a precision cutting and stamping speed of 30mm / s to 50mm / s, a cutting feed rate of 2.0mm to 3.0mm, a die preheating compensation temperature of 150℃ to 200℃, and a holding time of 3s to 5s. The secondary residual heat working condition corresponds to a precision cutting and punching speed of 20mm / s~30mm / s, a cutting feed rate of 1.5mm~2.5mm, a mold preheating compensation temperature of 200℃~250℃, and a holding pressure time of 5s~7s; The three-level residual heat working condition corresponds to a precision cutting and stamping speed of 10mm / s to 20mm / s, a cutting feed rate of 1.0mm to 2.0mm, a mold preheating compensation temperature of 250℃ to 300℃, and a holding pressure duration of 6s to 8s.

7. The method according to claim 1, characterized in that, The S7 integrated forged hot-cut near-net-shape body includes the following steps: For loading and positioning, the robot arm places the homogeneous and stable blank into the positioning cavity of the precision cutting die, with the blank tread surface facing up and the nut mounting surface facing down. The positioning pin is inserted into the process hole of the blank to achieve circumferential positioning. After positioning, the offset of the blank in each direction is ≤0.5mm. Flash removal: As the press slide moves downward, the flash removal punch first contacts the outer edge of the blank and removes the flash at a matching precision punching speed. The removed flash is then discharged from below the die. For tread surface finishing, the slide continues to descend 2mm to 5mm, and the tread surface finishing punch contacts the blank tread surface. The hot finishing of the tread surface is completed with a matching cutting feed rate. The cutting feed rate for tread surface finishing is determined according to the residual heat condition level. The nut mounting surface is shaped, and the slider continues to descend to the bottom dead center. The nut mounting surface shaping punch contacts the nut mounting surface to complete the hot shaping. The pressure is held for 3 to 8 seconds. The input state is the tread forming blank. After the mold is opened and the material is discharged, the slide returns to the top dead center, the ejector rod pushes the blank out of the mold cavity, the robot arm holds the blank and transfers it to the residual heat treatment station.

8. The method according to claim 1, characterized in that, The specific steps for waste heat treatment in S8 are as follows: After precision cutting, the blank is immediately quenched in water when the temperature is between 800℃ and 900℃. The quenching medium is a polymer aqueous solution with a mass fraction of 5% to 10%. After quenching, it is immediately placed in a tempering furnace at 180℃ to 250℃ for tempering. The tempering holding time is ≥120min.

9. The method according to claim 1, characterized in that, When the ambient temperature in the workshop is ≤10℃ and the convective wind speed is ≥1m / s, the S3 parameter acquisition shall be completed within 30s after the final forging is completed. The preheating compensation temperature of the precision cutting die shall be increased by 30℃~50℃ based on the die preheating compensation temperature corresponding to the residual heat condition level of the blank. The time for the blank to be transferred from the final forging station to the precision cutting station shall be ≤15s.

10. The method according to claim 7, characterized in that, The pressure for holding pressure is 80% to 100% of the precision cutting and stamping pressure. After the mold is opened, the blank is allowed to cool naturally in the air for ≤10 seconds before being transferred to the S8 residual heat treatment station.

Images