A method for controlling forming of a tee fitting in a precision forging process

Abstract

The present application belongs to the technical field of metal forging forming, and relates to a tee pipe fitting precision forging process forming control method. The present application collects the vertical punch load, the vertical punch actual displacement, the newly added filling volume in the stage target profile, the branch pipe root acoustic emission energy and the reference area acoustic emission energy in each forming control cycle, determines the forming stiffness, the filling efficiency and the acoustic emission energy difference; when the forming stiffness increases in turn, the filling efficiency decreases in turn and the acoustic emission energy difference increases in turn, the vertical punch advancing speed is reduced, the floating top material is paused and the horizontal punch back pressure is maintained; after adjustment, when the filling efficiency does not recover, the acoustic emission energy difference decreases in turn and the forming stiffness increases in turn, the vertical punch and the floating top material advancing are stopped and are sequentially unloaded. The present application can distinguish normal filling from abnormal filling caused by the compaction of the folded layers of the branch pipe inner wall, and can reduce the further compression of the folded interface and the closure caused by the continuous pressure compensation.

Description

Technical Field

[0001] This invention belongs to the field of metal forging technology, specifically relating to a method for controlling the forming process of precision forging of tee pipe fittings. Background Technology

[0002] Tee fittings are widely used in petrochemical, energy transmission, and high-pressure fluid pipelines. To improve the density and dimensional accuracy of tee fittings, current technology typically uses a horizontal punch to form the main pipe's inner hole and a vertical punch to form the branch pipe hole or branch pipe protrusion, using a floating ejector to push the metal from the junction area to the branch pipe region. Current forming control usually judges the filling degree of the branch pipe cavity based on the vertical punch load, vertical punch displacement, and the branch pipe's outer contour. When the vertical punch load continues to increase, the load increment corresponding to a unit vertical punch displacement increases, and the branch pipe height or branch pipe outer contour approaches the target value, it is usually determined that the branch pipe cavity has been completely filled, and then pressurization or pressure holding continues.

[0003] However, when the vertical punch advances too quickly, the floating top material starts too early, the temperature at the root of the branch pipe decreases, or the local frictional resistance increases, the metal in the junction area rolls back along the inner wall of the branch pipe, forming a folded layer on the inner wall of the branch pipe. As the vertical punch continues to advance, the folded layer on the inner wall of the branch pipe is gradually compressed, causing the forming stiffness to continuously increase, while the outer contour of the branch pipe can still gradually approach the target contour. Existing technology struggles to distinguish whether this increase in forming stiffness is caused by normal continuous metal filling or by the gradual compaction of the folded layer on the inner wall of the branch pipe, easily misjudging the compaction process of the folded layer as a normal filling process.

[0004] Following the aforementioned misjudgment, further increasing the vertical punch load, adding floating top material, or extending the holding time will not restore the already formed folded interface to a continuous metallic structure. Instead, it may further compress and seal the folded interface, causing interruption of the metal flow lines at the branch pipe root, insufficient effective load-bearing wall thickness, and internal layered defects. After the tee fitting has been subjected to pressure during service, the folded interface may expand to form cracks, affecting the load-bearing capacity and safety of the tee fitting. Therefore, current technology is still insufficient to accurately identify the abnormal filling process caused by the compaction of the folded layers on the inner wall of the branch pipe when the forming stiffness increases and the outer contour of the branch pipe approaches the target value, and to promptly stop further pressurization. Summary of the Invention

[0005] The purpose of this invention is to solve the problem that it is difficult to distinguish whether the increase in forming stiffness in the precision forging process of existing tee fittings is caused by continuous normal metal filling or by the gradual compaction of the folded layer on the inner wall of the branch pipe, which easily leads to the folded layer compaction process being misjudged as normal filling and pressure being added again. Therefore, a forming control method for the precision forging process of tee fittings is proposed.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for controlling the forming process of a tee pipe fitting through precision forging, comprising the following steps: collecting the vertical punch load, the actual displacement of the vertical punch, the newly added filling volume within the target contour of each forming control cycle, the acoustic emission energy at the root of the branch pipe, and the acoustic emission energy in the reference area.

[0007] The forming stiffness is determined based on the vertical punch load and the actual displacement of the vertical punch. The filling efficiency is determined based on the newly added filling volume within the target contour of the stage and the volume of the vertical punches. The acoustic emission energy difference between the acoustic emission energy at the root of the branch pipe and the acoustic emission energy in the reference area is also determined.

[0008] When the molding stiffness increases sequentially, the filling efficiency decreases sequentially, and the acoustic emission energy difference increases sequentially in multiple consecutive molding control cycles, the vertical punch advance speed is reduced, the floating top material is paused, and the horizontal punch back pressure is maintained.

[0009] After adjustment, when the filling efficiency in multiple consecutive molding control cycles is not higher than the filling efficiency of the last molding control cycle before adjustment, the acoustic emission energy difference decreases sequentially, and the molding stiffness increases sequentially, the vertical punch and floating top material advance are stopped, and the pressurization and unloading are stopped in the order of floating top material mechanism, vertical punch, and horizontal punch.

[0010] In summary, the beneficial effects of this invention, achieved through the adoption of the aforementioned method for controlling the precision forging process of tee fittings, are as follows: This invention determines the forming stiffness, filling efficiency, and acoustic emission energy difference, and jointly judges the direction of change of these three parameters within a continuous forming control cycle. This method solves the problem that judging the filling state solely based on the vertical punch load, vertical punch displacement, or the outer contour of the branch pipe can easily lead to misjudging the compaction of the folded layer on the inner wall of the branch pipe as normal filling; by identifying the inverse relationship between the increase in forming stiffness and the decrease in filling efficiency, it identifies the abnormal process where the vertical punch resistance increases but effective filling is not achieved.

[0011] This invention addresses the issue of whether to stop pressurization when the forming stiffness, filling efficiency, and acoustic emission energy difference increase sequentially. The method involves first reducing the vertical punch's advance speed, pausing the floating top material, and maintaining the horizontal punch's back pressure, while adjusting the changes in these three parameters. This approach distinguishes between temporary anomalies caused by mismatched advance speed or feeding rhythm and persistent anomalies caused by the compaction of the folded layers on the inner wall of the branch pipe. It reduces unnecessary interruptions caused by direct shutdowns and avoids continued pressurization under abnormal conditions.

[0012] This invention stops the vertical punch and floating ejector when the filling efficiency fails to recover after adjustment, the acoustic emission energy difference decreases sequentially, and the molding stiffness increases sequentially. It then stops pressurizing and unloading in the order of floating ejector mechanism, vertical punch, and horizontal punch. This method can terminate molding promptly when the activity at the folded interface weakens but the clamping resistance continues to increase, reducing further clamping and closure of the folded interface. Furthermore, sequential unloading reduces sudden metal backflow and mold impact in the junction area. Attached Figure Description

[0013] Figure 1 This is a flowchart of the precision forging process control method for tee fittings in this invention;

[0014] Figure 2 This is a flowchart illustrating the process of determining the acoustic emission energy difference in this invention.

[0015] Figure 3 This is a schematic diagram of the precision forging monitoring structure for the tee fitting in this invention. Detailed Implementation

[0016] The following will describe, with reference to the accompanying drawings of the embodiments of the present invention, a method for controlling the precision forging process of a tee pipe fitting according to the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1:

[0018] See Figure 1 - Figure 3 A method for controlling the forming process of a tee pipe fitting during precision forging includes: In this embodiment, a closed-loop control method based on forming stiffness, filling efficiency and acoustic emission energy difference is proposed to address the problem that during the precision forging process of a tee pipe fitting, the vertical punch load continuously increases after the folded layer on the inner wall of the branch pipe is gradually compressed, and the outer contour of the branch pipe is still gradually approaching the target contour, which is easily misjudged as normal filling of the branch pipe cavity.

[0019] The horizontal punch back pressure mentioned in this embodiment refers to the pressure exerted by the horizontal punch on the metal in the main pipe direction.

[0020] In one specific embodiment, such as Figure 3As shown, the tee fitting blank is placed inside the mold. A vertical punch is positioned above the branch pipe cavity and advances along the direction of the branch pipe cavity. Two horizontal punches are located on both sides of the tee fitting blank and advance towards it. A floating ejector mechanism is located below the tee fitting blank and applies material replenishment to the metal in the junction area. The arrows at the vertical punch, horizontal punches, and floating ejector mechanism indicate the corresponding advancing directions. A load sensor is positioned on the force transmission path of the vertical punch to collect the load on the vertical punch. A displacement sensor is positioned between the vertical punch and the mold to collect the actual displacement of the vertical punch. A first acoustic emission sensor is positioned on the outside of the mold corresponding to the root of the branch pipe to collect the acoustic emission energy at the root of the branch pipe. A second acoustic emission sensor is positioned on the outside of the mold away from the root of the branch pipe to collect the acoustic emission energy in the reference area. Figure 3 The setup shown allows the vertical punch load, the actual displacement of the vertical punch, the acoustic emission energy at the root of the branch pipe, and the acoustic emission energy in the reference area to be recorded synchronously within the same molding control cycle, providing a data basis for subsequent determination of molding stiffness and acoustic emission energy difference.

[0021] First, the following data are collected: vertical punch load, actual vertical punch displacement, newly added filling volume within the target contour of each stage, acoustic emission energy at the branch pipe root, and acoustic emission energy in the reference area. Then, the forming stiffness is determined based on the vertical punch load and actual vertical punch displacement; the filling efficiency is determined based on the newly added filling volume and the volume displaced by the vertical punch; and the acoustic emission energy difference between the branch pipe root and the reference area is determined. Further, when the forming stiffness continuously increases, the filling efficiency continuously decreases, and the acoustic emission energy difference continuously increases, the vertical punch advance speed is reduced, the floating top material is paused, and the horizontal punch back pressure is maintained. Finally, based on the changes in the adjusted filling efficiency, acoustic emission energy difference, and forming stiffness, the forming operation is resumed or continued pressure replenishment is stopped.

[0022] The continuous multiple molding control cycles are used to determine the continuous changing trend of molding stiffness, filling efficiency and acoustic emission energy difference; in one specific embodiment, three consecutive molding control cycles are used for judgment.

[0023] By combining the above-mentioned data collection, calculation, trial adjustment, and post-adjustment confirmation, the abnormal process of increased vertical punch resistance without effective filling can be identified, reducing the probability of misjudging the compaction of the folded layer on the inner wall of the branch pipe as normal cavity filling.

[0024] S1. Collect the vertical punch load, actual vertical punch displacement, newly added filling volume within the stage target contour, acoustic emission energy at the root of the branch pipe, and acoustic emission energy in the reference area during each forming control cycle.

[0025] Considering that during the precision forging of tee fittings within a closed die, it is impossible to directly observe the flow of metal in the junction area and the inner wall of the branch pipe, it is difficult to determine whether the load increase has truly resulted in additional filling based solely on the vertical punch load or the outer contour of the branch pipe. Therefore, this step simultaneously collects punch force, punch displacement, cavity filling, and acoustic emission signals from the root of the branch pipe, providing a basis for subsequent identification of the compaction of the folded layers on the inner wall of the branch pipe.

[0026] In one specific embodiment, after the vertical punch enters the branch pipe forming stage, the forming control cycle is divided according to a fixed vertical punch advance distance to reduce the impact of changes in the vertical punch advance speed on the comparability of data from different cycles.

[0027] First, a load sensor is installed on the force transmission path of the vertical punch, and a displacement sensor is installed between the vertical punch and the mold. The load on the vertical punch and the actual displacement of the vertical punch are collected and recorded synchronously.

[0028] Subsequently, the branch pipe cavity is divided into multiple contour segments along the branch pipe axis according to the vertical punch stroke. The volume of each contour segment is determined based on the target model of the tee fitting. Strain sensors are installed on the outer wall of the mold corresponding to each contour segment to collect the mold strain caused by metal contact and compression of the corresponding contour segment.

[0029] Furthermore, before batch precision forging, multiple tee fittings were trial-produced using the same material, billet size, and die. The trial-produced tee fittings were then sectioned, and the average die strain when the corresponding contour section was confirmed to be fully filled was determined as the filling strain for that contour section. Using an average value was to reduce the impact of individual tee fitting forming differences on the filling strain, ensuring a consistent basis for comparison of the filling strain used in each forming control cycle.

[0030] During the formal molding process, when the mold strain collected at the end of the current molding control cycle is not less than the filling strain of the corresponding contour segment, it is determined that the contour segment has reached the filling strain; the volumes of contour segments that have reached the filling strain in the current molding control cycle are accumulated to obtain the current filled contour segment volume; the volume of the filled contour segment in the previous molding control cycle is subtracted from the current filled contour segment volume to obtain the newly added filling volume in the stage target contour.

[0031] Finally, a first acoustic emission sensor is installed on the outside of the mold corresponding to the root of the branch pipe, and a second acoustic emission sensor is installed on the outside of the mold away from the root of the branch pipe. The acoustic emission energy at the root of the branch pipe and the acoustic emission energy in the reference area are collected respectively, and recorded synchronously with the load sensor and the displacement sensor.

[0032] S2. Determine the molding stiffness, filling efficiency, and acoustic emission energy difference.

[0033] Considering that the increase in vertical punch load could be caused by the normal filling of the branch tube cavity by metal or by the gradual compression of the folded layers on the inner wall of the branch tube, the load value alone cannot distinguish between the two situations. Therefore, this step establishes judgment parameters based on three aspects: the degree of punch obstruction, the degree of conversion of the displaced volume into the newly filled volume, and the local interface activity at the root of the branch tube.

[0034] In one specific embodiment, the method for determining the forming stiffness includes the following steps.

[0035] First, with no blank placed and the mold closed, multiple progressively increasing loads are applied to the vertical punch along the pushing direction. The actual displacement of the vertical punch corresponding to each load is recorded to form a correspondence between load and elastic displacement.

[0036] Subsequently, during the forming process of the tee fitting, based on the vertical punch load within the current forming control cycle, the corresponding elastic displacement is obtained from the corresponding relationship. The actual displacement of the current vertical punch is subtracted from the elastic displacement to obtain the blank forming displacement.

[0037] Furthermore, the forming stiffness of the current forming control cycle is determined by dividing the difference in vertical punch load between the current forming control cycle and the previous forming control cycle by the difference in billet forming displacement between the two forming control cycles, according to the following formula: This forming stiffness is used to reduce the impact of elastic deformation of the press frame, die, and vertical punch on the judgment results.

[0038] in, Indicates the first The forming stiffness of each forming control cycle, in kilonewtons per millimeter; Indicates the first The vertical punch load difference between each forming control cycle and the previous forming control cycle, in kilonewtons; Indicates the first The difference in billet forming displacement between the current forming control cycle and the previous forming control cycle, in millimeters; symbol This represents the difference in the corresponding quantities between two adjacent molding control cycles; It represents the sequence number of the molding control cycle and is a positive integer not less than 2.

[0039] The method for determining filling efficiency includes the following steps.

[0040] First, the cross-sectional area of ​​the vertical punch is multiplied by the actual displacement increment of the vertical punch within the current forming control cycle to obtain the vertical punch displacement volume. Then, the ratio of the newly added filling volume within the stage target contour to the vertical punch displacement volume is determined as the current volume conversion ratio. The corresponding ratio of tee fittings (confirmed by sectioning to have no branch pipe inner wall folds) within the same vertical punch stroke range is determined as the reference volume conversion ratio. Finally, the ratio of the current volume conversion ratio to the reference volume conversion ratio is determined as the filling efficiency. A continuously decreasing filling efficiency indicates a continuous decrease in the newly added filling volume relative to the normal filling process.

[0041] See Figure 2 The method for determining the acoustic emission energy difference includes steps S101 to S103.

[0042] S101. A first acoustic emission sensor is set on the outside of the mold corresponding to the root of the branch pipe, and a second acoustic emission sensor is set on the outside of the mold away from the root of the branch pipe, to collect the acoustic emission energy at the root of the branch pipe and the acoustic emission energy in the reference area, respectively.

[0043] S102. During the blankless mold closing process, the ratio of acoustic emission energy of the first acoustic emission sensor and the second acoustic emission sensor is used as the reference correction coefficient, and the time difference between the signals of the two acoustic emission sensors arriving at the reference is determined based on the common impact signal.

[0044] S103. Within each molding control cycle, the acoustic emission signals collected by the first acoustic emission sensor and the second acoustic emission sensor are time-aligned according to the time difference of the arrival of the signal reference. Pulses whose occurrence time difference after time alignment does not exceed the acoustic emission signal sampling interval are identified as common vibration pulses and discarded. The squares of the voltage amplitudes of the remaining pulses are accumulated according to the sampling interval to obtain the first effective acoustic emission energy and the second effective acoustic emission energy. The acoustic emission energy difference is obtained by subtracting the product of the second effective acoustic emission energy and the reference correction coefficient from the first effective acoustic emission energy.

[0045] S3. When the molding stiffness increases sequentially, the filling efficiency decreases sequentially, and the acoustic emission energy difference increases sequentially in multiple consecutive molding control cycles, reduce the vertical punch advance speed, pause the floating top material, and maintain the horizontal punch back pressure.

[0046] Considering that when the folds on the inner wall of the branch pipe are just formed, slippage and friction may still occur at the fold interface, which would enhance the acoustic emission activity at the root of the branch pipe; at the same time, the fold layer would hinder the metal from continuing to enter the target contour of the stage, which would increase the forming stiffness and reduce the filling efficiency. Therefore, this step does not directly stop the machine when a single parameter is abnormal, but rather implements exploratory adjustments based on the coordinated changes of the three parameters over multiple consecutive forming control cycles.

[0047] In one specific embodiment, three consecutive molding control cycles that meet the judgment conditions are determined as the first judgment cycle, the second judgment cycle, and the third judgment cycle in chronological order. Using three consecutive molding control cycles is to simultaneously generate two adjacent comparisons, avoiding adjustments based solely on numerical changes in a single molding control cycle.

[0048] First, determine whether the molding stiffness of the second judgment cycle is greater than the molding stiffness of the first judgment cycle, and whether the molding stiffness of the third judgment cycle is greater than the molding stiffness of the second judgment cycle.

[0049] Subsequently, it is determined whether the filling efficiency of the second judgment cycle is less than that of the first judgment cycle, and whether the filling efficiency of the third judgment cycle is less than that of the second judgment cycle.

[0050] Furthermore, it is determined whether the acoustic emission energy difference in the second judgment period is greater than the acoustic emission energy difference in the first judgment period, and whether the acoustic emission energy difference in the third judgment period is greater than the acoustic emission energy difference in the second judgment period.

[0051] When all of the above judgments are true, the stiffness increase rate and efficiency decrease rate are determined by the first and last molding control cycles among the multiple consecutive molding control cycles that trigger the adjustment; in this embodiment, the first molding control cycle is the first judgment cycle and the last molding control cycle is the third judgment cycle.

[0052] The stiffness increase rate, efficiency decrease rate, speed reduction ratio, and adjusted vertical punch propulsion speed are determined using the following formulas: .

[0053] in, , These represent the forming stiffness of the first and third judgment cycles, respectively. , These represent the filling efficiency of the first and third judgment cycles, respectively. This represents the rate of increase in the forming stiffness of the third judgment cycle relative to the forming stiffness of the first judgment cycle. This indicates the rate of decrease in filling efficiency in the first judgment cycle relative to the filling efficiency in the third judgment cycle. This represents the percentage decrease in speed; it is a dimensionless number and ranges from 0 to 0.5. This indicates taking the maximum value between the stiffness increase rate and the efficiency decrease rate; This means taking the smaller value between the maximum value and 0.5; This indicates the adjusted vertical thrust speed of the punch, expressed in millimeters per second. The vertical thrust velocity of the punch in the third judgment cycle is expressed in millimeters per second. This indicates the percentage of the adjusted vertical punch advance speed relative to the vertical punch advance speed in the third judgment cycle.

[0054] The speed reduction ratio is taken as the maximum value between the stiffness increase rate and the efficiency decrease rate, so that the degree of reduction in the vertical punch propulsion speed corresponds to the parameter with more obvious changes; the upper limit of the speed reduction ratio is set to 0.5 to avoid the vertical punch propulsion speed being reduced too much at once, while retaining the propulsion process required to continue comparing filling efficiency, acoustic emission energy difference and forming stiffness after adjustment.

[0055] After completing the above calculations, the adjusted vertical punch advance speed is reduced from the vertical punch advance speed of the third judgment cycle according to the speed reduction ratio. The vertical punch is controlled to continue advancing at the adjusted advance speed, keeping the floating top material at the position at the end of the third judgment cycle, and maintaining the horizontal punch back pressure at the level at the end of the third judgment cycle.

[0056] Reducing the vertical punch advance speed is used to decrease the instantaneous amount of metal squeezed into the branch pipe area; pausing the floating top material is used to stop the continued feeding of metal into the junction area; maintaining the horizontal punch back pressure is used to maintain the main pipe direction constraint and avoid the metal in the junction area moving in the opposite direction of the main pipe due to the synchronous reduction of the horizontal punch back pressure.

[0057] S4. Determine whether to resume molding or stop further pressurization based on the adjusted filling efficiency, acoustic emission energy difference, and molding stiffness.

[0058] Considering that excessively fast vertical punch advance speed or mismatch in the feeding rhythm of the floating top material may temporarily cause an increase in molding stiffness and a decrease in filling efficiency, directly stopping the machine based solely on the abnormal trend before adjustment may increase the number of unnecessary shutdowns. This step distinguishes between recoverable material supply mismatch processes and unrecoverable folding layer compaction processes by observing multiple molding control cycles after the trial adjustment.

[0059] In one specific embodiment, the three consecutive forming control cycles after reducing the vertical punch advance speed are determined as the first recovery cycle, the second recovery cycle, and the third recovery cycle according to their time sequence.

[0060] When the filling efficiency of the second recovery cycle is greater than that of the first recovery cycle, the filling efficiency of the third recovery cycle is greater than that of the second recovery cycle, and the molding stiffness of the second recovery cycle is not greater than that of the first recovery cycle, and the molding stiffness of the third recovery cycle is not greater than that of the second recovery cycle, it is determined that the additional filling after the trial adjustment has been restored.

[0061] At this point, the vertical punch advance speed is gradually increased, and the filling efficiency and forming stiffness are judged in each forming control cycle. When the filling efficiency does not decrease and the forming stiffness does not increase, the vertical punch advance speed is further increased until it is restored to the vertical punch advance speed before adjustment, and the floating top material is started.

[0062] When the filling efficiency of the first, second, and third recovery cycles is not greater than the filling efficiency of the third judgment cycle, the acoustic emission energy difference of the second recovery cycle is less than the acoustic emission energy difference of the first recovery cycle, the acoustic emission energy difference of the third recovery cycle is less than the acoustic emission energy difference of the second recovery cycle, and the forming stiffness of the second recovery cycle is greater than the forming stiffness of the first recovery cycle and the forming stiffness of the third recovery cycle is greater than the forming stiffness of the second recovery cycle, it is determined that after reducing the vertical punch advance speed and pausing the floating top material, the additional filling has not yet recovered.

[0063] Among these, the failure to recover filling efficiency indicates that the volume displaced by the vertical punch has not been converted back into the new filling volume within the target contour of the stage; the continuous decrease in acoustic emission energy difference indicates that the local interface activity at the root of the branch pipe is gradually weakening; and the continued increase in forming stiffness indicates that the resistance experienced by the vertical punch is still increasing. All three factors together indicate that the continuously increasing resistance has not promoted the normal filling of the branch pipe cavity, but may have originated from the gradual compaction of the folded layers on the inner wall of the branch pipe.

[0064] When the above conditions are met, stop the vertical punch and floating top material advance, and implement sequential unloading.

[0065] First, maintain the back pressure of the horizontal punch and reduce the load of the floating ejector to zero; then, reduce the load of the vertical punch in sequence until the load of the vertical punch is zero; finally, reduce the back pressure of the horizontal punch to zero to complete the unloading of the tee fitting and the mold.

[0066] Specific control examples.

[0067] In one specific embodiment, three molding control cycles that simultaneously satisfy the following conditions for the first time from continuously recorded molding control cycles are selected as the first judgment cycle, the second judgment cycle, and the third judgment cycle. The molding stiffness of the three judgment cycles are 8.4 kN / mm, 9.1 kN / mm, and 10.0 kN / mm, respectively; the filling efficiencies are 0.92, 0.81, and 0.69, respectively; and the acoustic emission energy differences are... volts squared seconds volts squared seconds and Volts squared seconds. The above values ​​are not preset judgment thresholds, but are used to reflect the direction of change of the three parameters in the continuous molding control cycle.

[0068] First, the stiffness increase rate was calculated to be 0.190 based on the forming stiffness of the first and third judgment cycles. Then, the efficiency decrease rate was calculated to be 0.250 based on the filling efficiency of the first and third judgment cycles. Since the efficiency decrease rate is greater than the stiffness increase rate, the speed reduction ratio was set to 0.250, ensuring that the reduction in vertical punch speed corresponds more significantly to the decrease in filling efficiency. Therefore, reducing the vertical punch speed by 25%, while pausing the floating top material and maintaining the horizontal punch back pressure, helps reduce the impact of continued rapid advancement and material replenishment on the judgment results, and retains the main directional constraint for the adjusted continuous comparison.

[0069] After adjustment, three consecutive forming control cycles after reducing the vertical punch advance speed were selected as the first, second, and third recovery cycles. The filling efficiencies of the three recovery cycles were 0.68, 0.66, and 0.65, respectively, none of which were higher than the filling efficiency of 0.69 in the third judgment cycle before adjustment; the acoustic emission energy differences were respectively... volts squared seconds volts squared seconds and The molding stiffness was 10.3 kN / mm, 10.7 kN / mm, and 11.2 kN / mm, respectively. Three consecutive molding control cycles after adjustment were selected to sequentially confirm whether the filling efficiency had recovered, whether the acoustic emission energy difference had decreased, and whether the molding stiffness had continued to increase, using the same comparison method as before adjustment.

[0070] Therefore, the filling efficiency of the three recovery cycles is first compared with the filling efficiency of the third judgment cycle, and then the acoustic emission energy difference and molding stiffness of the three recovery cycles are compared sequentially. When the filling efficiency fails to recover, the acoustic emission energy difference decreases sequentially, and the molding stiffness increases sequentially, the vertical punch and floating top material advance are stopped, and the pressurization and unloading are stopped in the order of floating top material mechanism, vertical punch, and horizontal punch. By adopting the above comparison sequence, molding can be stopped only due to the increase in molding stiffness or the change in acoustic emission energy difference, so that the stop control is based on the common change of the newly added filling not recovering after adjustment and the folded layer continuing to be compressed.

[0071] This specific control process can prevent further increasing the vertical punch load or increasing the amount of floating top material from further compressing and sealing the already formed inner wall folded layer of the branch pipe.

[0072] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the present invention's method for controlling the precision forging process of a tee fitting and its inventive concept, should be covered within the scope of protection of the present invention.

Claims

1. A method for controlling the forming process of a precision forging tee pipe fitting, characterized in that, Includes the following steps: Collect the vertical punch load, actual vertical punch displacement, newly added filling volume within the stage target contour, acoustic emission energy at the root of the branch pipe, and acoustic emission energy in the reference area during each forming control cycle; The forming stiffness is determined based on the vertical punch load and the actual displacement of the vertical punch; the filling efficiency is determined based on the newly added filling volume within the target contour of the stage and the volume of the vertical punches; and the acoustic emission energy difference is determined based on the acoustic emission energy at the root of the branch pipe and the acoustic emission energy in the reference area. When the molding stiffness increases sequentially, the filling efficiency decreases sequentially, and the acoustic emission energy difference increases sequentially during a continuous molding control cycle, the vertical punch advance speed is reduced, the floating top material is paused, and the horizontal punch back pressure is maintained. After adjustment, when the filling efficiency is not higher than that of the last molding control cycle before adjustment, the acoustic emission energy difference decreases sequentially, and the molding stiffness increases sequentially in a continuous molding control cycle, the vertical punch and floating top material advance are stopped, and the pressurization and unloading are stopped in the order of floating top material mechanism, vertical punch, and horizontal punch.

2. The method for controlling the forming process of a tee pipe fitting during precision forging according to claim 1, characterized in that, The last molding control cycle before the adjustment is determined as the adjustment reference cycle; When the filling efficiency of the adjusted continuous forming control cycle is no greater than the filling efficiency of the adjusted reference cycle, the acoustic emission energy difference decreases sequentially, and the forming stiffness increases sequentially, the vertical punch and floating top material advance are stopped.

3. The method for controlling the forming process of a tee pipe fitting during precision forging according to claim 2, characterized in that, Methods for determining acoustic emission energy difference include: A first acoustic emission sensor is installed on the outside of the mold corresponding to the root of the branch pipe, and a second acoustic emission sensor is installed on the outside of the mold away from the root of the branch pipe. During the blankless mold closing process, the ratio of acoustic emission energy of the first acoustic emission sensor to that of the second acoustic emission sensor is used as the reference correction coefficient. Within each molding control cycle, the acoustic emission energy of the second acoustic emission sensor is corrected using a reference correction coefficient, and the difference between the acoustic emission energy of the first acoustic emission sensor and the corrected acoustic emission energy of the second acoustic emission sensor is used as the acoustic emission energy difference.

4. The method for controlling the forming process of a tee pipe fitting during precision forging according to claim 1, characterized in that, Methods for collecting vertical punch load, actual vertical punch displacement, newly added filling volume within the stage target contour, acoustic emission energy at the branch pipe root, and acoustic emission energy in the reference area during each forming control cycle include: A load sensor is installed on the force transmission path of the vertical punch, and a displacement sensor is installed between the vertical punch and the mold to collect the load and actual displacement of the vertical punch, respectively. The branch pipe cavity is divided into multiple contour sections according to the vertical punch stroke. The contour of the contour section corresponding to the current forming control cycle is determined as the stage target contour. Strain sensors are set on the outer wall of the mold corresponding to each contour section. The mold strain when the tee fitting, which has been confirmed by cutting to have no folds in the inner wall of the branch pipe, is filled into each contour section is taken as the filling strain. The sum of the volumes of contour segments that reach filling strain in the next molding control cycle minus the sum of the volumes of contour segments that reach filling strain in the previous molding control cycle yields the new filling volume within the target contour of the stage. A first acoustic emission sensor and a second acoustic emission sensor are respectively installed at the root of the branch pipe and on the outside of the mold away from the root of the branch pipe to simultaneously collect the acoustic emission energy at the root of the branch pipe and the acoustic emission energy in the reference area.

5. The method for controlling the forming process of a tee pipe fitting during precision forging according to claim 1, characterized in that, Methods for determining forming stiffness based on vertical punch load and actual vertical punch displacement include: When no blank is placed and the mold is closed, establish the correspondence between the vertical punch load and the elastic displacement; In the forming process of tee fittings, the difference between the actual displacement of the vertical punch and the corresponding elastic displacement is taken as the blank forming displacement, and the ratio of the difference in vertical punch load to the difference in blank forming displacement in adjacent forming control cycles is taken as the forming stiffness.

6. The method for controlling the forming process of a tee pipe fitting during precision forging according to claim 1, characterized in that, Methods for determining filling efficiency based on the newly added filling volume within the target outline and the volume displaced by the vertical punches include: The product of the cross-sectional area of ​​the vertical punch and the actual displacement difference of the vertical punch in the adjacent forming control cycle is used as the vertical punch displacement volume, and the ratio of the newly added filling volume within the stage target contour to the vertical punch displacement volume is used as the current volume conversion ratio. The ratio of the newly added filling volume to the vertical punch displacement volume within the stage target contour of the tee fitting, which has been confirmed by sectioning to have no folds in the inner wall of the branch pipe, to the ratio of the volume of the tee fitting to the volume of the vertical punch, within the vertical punch stroke range corresponding to the current forming control cycle, is used as the reference volume conversion ratio. The filling efficiency is defined as the ratio of the current volume conversion ratio to the reference volume conversion ratio.

7. The method for controlling the forming process of a tee pipe fitting during precision forging according to claim 3, characterized in that, Methods for determining the acoustic emission energy difference between the acoustic emission energy at the root of the branch pipe and the acoustic emission energy in the reference region include: The arrival time difference of the signal is determined based on the common impact signal during the blankless mold closing process. The acoustic emission signals collected by the first acoustic emission sensor and the second acoustic emission sensor are time-aligned based on the arrival time difference of the signal. Pulses whose occurrence time difference after time alignment does not exceed the acoustic emission signal sampling interval are identified as common vibration pulses and discarded. The squared voltage amplitudes of the remaining pulses are accumulated according to the sampling interval to obtain the first effective acoustic emission energy and the second effective acoustic emission energy. The acoustic emission energy difference is obtained by subtracting the product of the second effective acoustic emission energy and the reference correction coefficient from the first effective acoustic emission energy.

8. The method for controlling the forming process of a tee pipe fitting during precision forging according to claim 1, characterized in that, When, during a continuous molding control cycle, the molding stiffness increases sequentially, the filling efficiency decreases sequentially, and the acoustic emission energy difference increases sequentially, methods for reducing the vertical punch advance speed, pausing the floating top material, and maintaining the horizontal punch back pressure include: The ratio of the difference in molding stiffness between the last molding control cycle and the first molding control cycle in the continuous molding control cycle that triggers adjustment to the molding stiffness of the first molding control cycle is determined as the stiffness increase rate, and the ratio of the difference in filling efficiency between the first molding control cycle and the last molding control cycle to the filling efficiency of the first molding control cycle is determined as the efficiency decrease rate. The maximum value between the stiffness increase rate and the efficiency decrease rate is taken as the speed reduction ratio; Reduce the vertical punch advance speed according to the speed reduction ratio, and maintain the floating top material position and horizontal punch back pressure at the trigger adjustment.

9. The method for controlling the forming process of a tee pipe fitting during precision forging according to claim 8, characterized in that, After reducing the vertical punch advance speed according to the speed reduction ratio, when the filling efficiency increases sequentially and the forming stiffness does not increase sequentially in the continuous forming control cycle, the vertical punch advance speed is gradually increased until it is restored to the vertical punch advance speed before adjustment, and the floating top material is started.

10. The method for controlling the forming process of a tee pipe fitting during precision forging according to claim 2, characterized in that, After stopping the vertical punch and floating top material advance, maintain the back pressure of the horizontal punch and reduce the pressure of the floating top material to zero; Then, the vertical punch load is gradually reduced until it is zero, and then the horizontal punch back pressure is reduced to zero.

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