Upsetting heating electrode based on shape heat dynamic matching, plate forging tool and process

Abstract

The invention discloses upsetting heating electrodes based on shape heat dynamic matching, a plate forging tool and a process, and belongs to the field of metal plastic forming equipment. According to the deformation requirements of different areas of a forming material, the plate forging tool comprising a plurality of upsetting heating electrodes is adopted; when a second part of an electrode core rod in the upsetting heating electrode stretches into an electrode shell, a reset spring device is compressed, an electric contact part makes contact with an annular resistor, a conductive column, the annular resistor, the electric contact part and the electrode core rod are electrically connected, and when the second part of the electrode core rod continues to stretch into the electrode shell, the electric contact part is separated from the annular resistor; and the electric connection between the electrode core rod and the conductive column is disconnected. The heating temperature of the upsetting heating electrode is actively matched with the geometrical morphology of the blank in the blank forming process, the temperature is high when the deformation amount is large, the temperature is low when the deformation amount is small, and accurate temperature control in the blank forming process is achieved. The length of each annular resistor of the plate forging tool is matched with the target shape of the part, the part does not need to be completely heated, and energy consumption is reduced.

Description

Technical Field

[0001] This invention relates to metal plastic forming equipment, specifically to an upsetting heating electrode, plate forging tooling, and process based on dynamic matching of form and heat. Background Technology

[0002] Thermoforming technology is widely used due to its ability to effectively improve the plastic deformation capacity of materials. In existing technologies, traditional processes generally employ high-temperature box furnaces and other equipment to heat the entire workpiece to the forming temperature, resulting in significantly low thermal efficiency and substantial energy waste. The fundamental reason is that the overall heating mode cannot differentiate between the different deformation requirements of the material, and high-temperature heating of low-deformation areas is essentially ineffective energy consumption. To improve energy consumption, some improvement schemes propose using local induction heating methods, but this technology still has inherent limitations: the induction heating area relies on the fixed physical positioning of the induction coil, lacking spatial adjustability and unable to dynamically adapt to the real-time changes in strain distribution during the forming process. This leads to high-strain areas experiencing insufficient heating and excessively high deformation resistance, while low-strain areas suffer from overheating, causing flow hysteresis effects and resulting in material folding or abnormal thinning. Summary of the Invention

[0003] Purpose of the invention: To address the above-mentioned shortcomings, this invention provides an upsetting heating electrode, plate forging tooling, and plate forging process based on dynamic matching of form and heat to improve energy consumption control and forming quality.

[0004] Technical Solution: To solve the above problems, the present invention provides an upsetting heating electrode based on dynamic shape-thermal matching, comprising an electrode shell, an electrode core rod, a return spring device, an insulating ring, an annular resistor, a conductive post, and a power device. The inner wall of the electrode shell is provided with an annular resistor. The electrode core rod comprises a first part and a second part fixedly connected in sequence. The end of the first part of the electrode core rod is used to contact the blank. The second part of the electrode core rod extends into the electrode shell and moves along the electrode shell. An insulating layer is provided on the outer periphery of the second part of the electrode core rod. An electrical contact part is provided at the end of the second part of the electrode core rod for electrical contact with the annular resistor on the inner wall of the electrode shell. The electrical contact part and the electrode shell... A reset spring device and a power device are provided between the electrode core rod and the electrode housing. The power device is used to drive the electrode core rod to move along the electrode housing. The length of the electrode housing is longer than the length of the second part of the electrode core rod. The electrode housing is provided with a conductive post. One end of the conductive post is electrically connected to a ring resistor, and the other end of the conductive post extends out of the electrode housing to connect to an external circuit. When the second part of the electrode core rod extends into the electrode housing, the reset spring device is compressed, and the electrical contact part contacts the ring resistor. The conductive post, the ring resistor, the electrical contact part, and the first and second parts of the electrode core rod form an electrical connection. When the second part of the electrode core rod continues to extend into the electrode housing, the electrical contact part disengages from the ring resistor, and the electrical connection between the electrode core rod and the conductive post is broken.

[0005] Furthermore, the electrode core rod has a stepped structure with the outer diameter of the first part being larger than that of the second part, and the outer diameter of the first part of the electrode core rod is larger than the inner diameter of the electrode shell, so that the first part of the electrode core rod cannot extend into the electrode shell. The electrode core rod is made of a material with high thermal conductivity and high electrical conductivity to reduce Joule heat loss and improve the electrical energy to heat energy conversion efficiency.

[0006] Furthermore, an insulating ring is provided inside the electrode housing, and the insulating ring is located at the front end of the annular resistor. When the second part of the electrode core rod extends into the electrode housing, the electrical contact part first contacts the insulating ring. When the second part of the electrode core rod continues to extend in, the electrical contact part then contacts the annular resistor.

[0007] Furthermore, the power device includes a hydraulic rod and a hydraulic control system. The hydraulic rod includes several hydraulic units arranged in sequence. One end of the hydraulic rod is fixedly connected to the electrical contact part of the electrode core rod, and the other end is fixedly connected to the electrode shell. The electrode shell is provided with inlet and outlet ports, which correspond to the inlet and outlet ports of the hydraulic rod. The hydraulic control system controls the extension and retraction of the hydraulic rod through the inlet and outlet ports of the electrode shell. The hydraulic rod is installed as a whole on the inner ring of the spring.

[0008] The present invention discloses a plate forging fixture based on dynamic matching of form and heat, comprising an electrode head device, a mold, and an external circuit. The electrode head device includes several upsetting heating electrodes as described above. The mold includes a support mold and a forming mold. The support mold is used to fix the billet. The forming mold is disposed on the forming surface of the billet and is used to form the billet. The forming mold is provided with several through holes for the first part of the electrode core to extend into. After the first part of the electrode core extends into the through holes, it contacts the billet. The conductive posts of the billet and the upsetting heating electrodes are connected to the external circuit. The annular resistance length of each upsetting heating electrode is determined according to the distance from the initial plane of the billet to the forming surface of the forming mold. When the billet is completely attached to the forming mold, the electrical contact part of the electrode core disengages from the annular resistance.

[0009] Furthermore, the surface of the mold is coated with an insulating layer, which is an insulating coating or an insulating sleeve. The supporting mold includes a rear mold, a lower pad, and a lower pad support frame. The rear mold is used to install on the rear end of the blank; the lower pad is used to install on the lower surface end of the electrode head device; the lower pad support frame is disposed on the upper part of the lower pad to support the electrode head device.

[0010] Furthermore, a thermocouple is embedded in the first part of the electrode mandrel. The thermocouple is used to provide real-time feedback on the temperature of the interface between the electrode mandrel and the billet. The thermocouple (sensor) is connected to a PID closed-loop control system to prevent excessively high local temperatures from affecting the surface quality of the billet. The upsetting heating electrode array of the electrode head device is arranged such that the electrical parameters of the upsetting heating electrodes in the array are independently adjustable, and a programmable power supply can be set. Different currents can be set for the optimal forming temperature of parts with different thicknesses and materials.

[0011] The plate forging process described herein, employing the aforementioned plate forging fixture based on dynamic shape-thermal matching, includes the following steps:

[0012] Step 1: Determine the blank parameters and target workpiece parameters, and obtain the forming die parameters;

[0013] Step 2: Perform simulation design based on the forming mold parameters, blank parameters and target workpiece parameters to obtain the annular resistance length of each upsetting heating electrode and the processing control parameters;

[0014] Step 3: Based on the forming die parameters and the annular resistance length of each upsetting heating electrode, obtain the die and electrode head device, and install the blank, die, electrode head device and external circuit.

[0015] Step 4: Start the hydraulic press for upsetting and set the processing parameters according to the processing control parameters;

[0016] Step 5: As the upsetting process proceeds, the electrode core moves backward along the electrode shell, the length of the current flowing through the annular resistor gradually increases, and the corresponding current gradually decreases; when the hydraulic head of the hydraulic press reaches the distance threshold close to the electrode core, the power device is controlled to retract the electrode core that has reached the distance threshold to prevent the hydraulic head from damaging the electrode core; when the blank at the upsetting heating electrode contact part is attached to the forming mold, the electrical contact part of the electrode core disengages from the annular resistor, and the current loop is broken;

[0017] Step 6: Repeat step 5 until the processing is complete.

[0018] Furthermore, the simulation design process includes the following steps:

[0019] Step 21: Based on the billet parameters and target workpiece parameters, simulate the entire bending-upsetting process using finite element simulation software, extract the equivalent plastic strain field distribution and workpiece deformation field data in the finite element simulation software; determine the threshold of equivalent plastic strain based on the billet parameters, and determine the high strain zone and low strain zone of the billet based on the threshold.

[0020] Step 22: Obtain the strain gradient during the billet forming process based on the equivalent plastic strain field distribution. Using the mapping model between the temperature field and the equivalent plastic strain gradient, generate the target temperature distribution function based on the amplitude of the strain gradient, and convert the strain gradient during the billet forming process into a temperature control command.

[0021] Step 23: Based on the target forming temperature of different areas of the billet, generate a process parameter table containing the coordinates of each upsetting heating electrode, the current amplitude of each upsetting heating electrode, and the heating time using the temperature rise calculation formula;

[0022] Step 24: Perform the thermo-mechanical coupling verification process. Construct an electrothermal-structural multiphysics model in the finite element simulation software: import the parameters from the process parameter table, simulate the Joule heating effect, rerun the simulation of bending-upsetting process, and collect new equivalent plastic strain field data. Calculate the standard deviation of the equivalent plastic strain and the maximum mold gap value in the whole field.

[0023] Step 25: Perform uniformity compliance judgment: When the standard deviation of equivalent plastic strain meets the uniformity requirements and the maximum mold gap is compliant, the process is judged to be compliant and the final process parameter table is output; if the process is not compliant, return to step 22 and perform iterative optimization with the new equivalent plastic strain field distribution as input until the process is compliant.

[0024] Furthermore, the billet is a material that is difficult to deform at room temperature, including titanium alloys, aluminum alloys, and high-strength steel, and the plate thickness can be 40-150mm. If the initial shape of the billet is plate-shaped, the height-to-width ratio should be less than 2.5; if it is cylindrical, the height-to-diameter ratio should be less than 3.

[0025] Beneficial effects: Compared with the prior art, the significant advantages of this invention are: the heating temperature of the upsetting heating electrode actively matches the geometry of the billet during the billet forming process, providing a higher temperature when the required deformation is large and a lower temperature when the required deformation is small, thus achieving precise temperature control during the billet forming process. The heating electrode is promptly de-energized after forming, which is more accurate than judging whether processing is complete based on methods such as time, reducing energy consumption.

[0026] The electrode array of the plate forging fixture can independently control the length of each electrode ring resistor according to the target shape of the formed part to achieve active matching with the target geometry of the formed part. This ensures that the local heating area and the high strain area of ​​the material form a precise spatial mapping, and the local temperature field is controlled to match the material deformation state. It is not necessary to heat the entire part, which can reduce energy consumption, reduce the ineffective heating area and reduce the overall energy consumption, thereby achieving energy consumption control and improved forming quality.

[0027] Compared to traditional overall heating or fixed-zone heating technologies, this method employs a feedforward control strategy to achieve precise heating. Electrode current parameters are pre-calculated based on the PEEQ gradient distribution, and combined with a split-electrode temperature control method, the current is concentrated to provide localized heating, generating stress relaxation and reducing overall energy consumption. The temperature field is constructed using pre-generated PEEQ field data from finite element simulation, eliminating the need for a real-time temperature sensing feedback system, simplifying the hardware architecture and reducing system complexity. Attached Figure Description

[0028] Figure 1 This is a cross-sectional view of the upsetting heating electrode of the present invention in its initial uncompressed state.

[0029] Figure 2 This is a cross-sectional view of the upsetting heating electrode of the present invention in a compressed state.

[0030] Figure 3 This is a schematic diagram of the overall structure of the upsetting heating electrode of the present invention.

[0031] Figure 4 This is a schematic diagram of the simulation process in this invention.

[0032] Figure 5 This is a schematic diagram illustrating the morphological changes of the blank as it is processed into the target part in this invention.

[0033] Figure 6 This is a schematic diagram of the initial state of the plate forging fixture in this invention.

[0034] Figure 7 This is a schematic diagram of the annular resistance length of the upsetting heating electrode at different positions in this invention.

[0035] Figure 8 This is a schematic diagram of the intermediate processing state of the billet in this invention.

[0036] Figure 9 This is a local temperature diagram of parts and tool heads in different areas of the billet during intermediate processing in this invention.

[0037] Figure 10 This is a schematic diagram of the structure of the part in the formed state in this invention.

[0038] Electrode core rod 1; insulating ring 2; conductive post 3; ring resistor 4; electrode shell 5; reset spring device 6; first insulating layer 7; lower pad 8; lower pad support frame 9; forming mold 10; rear mold 11; electrode head device 12; second insulating layer 13; blank 14; hydraulic rod 201; liquid 202. Detailed Implementation

[0039] Example 1

[0040] like Figures 1 to 3As shown, this embodiment of an upsetting heating electrode based on dynamic shape-thermal matching includes an electrode shell 5, an electrode core 1, a return spring device 6, an insulating ring 2, an annular resistor 4, a conductive post 3, and a power device. An annular resistor is provided on the inner wall of the electrode shell 5. The electrode core 1 includes a first part and a second part fixedly connected in sequence. The electrode core 1 has a stepped structure where the outer diameter of the first part is larger than the outer diameter of the second part. The end of the first part of the electrode core 1 is used to contact the blank. The second part of the electrode core 1 extends into the electrode shell 5 and moves along the electrode shell 5. The outer diameter of the first part of the electrode core 1 is larger than the inner diameter of the electrode shell 5. The first part of the electrode core 1 cannot extend into the inner diameter of the electrode shell 5. In the electrode housing 5, a first insulating layer 7 is provided on the outer periphery of the second part of the electrode core rod 1. The first insulating layer 7 is an insulating coating or an insulating sleeve. An electrical contact part is provided at the end of the second part of the electrode core rod 1 for electrical contact with the annular resistor on the inner wall of the electrode housing 5. A reset spring device and a power device are provided between the electrical contact part and the electrode housing 5. The reset spring device 6 is housed in the electrode housing 5. The power device is used to drive the electrode core rod to move along the electrode housing. The length of the electrode housing 5 is longer than the length of the second part of the electrode core rod 1. A conductive post 3 is provided on the electrode housing. One end of the conductive post 3 is electrically connected to the annular resistor, and the other end of the conductive post extends out of the electrode housing for connecting to an external circuit.

[0041] When the second part of the electrode core rod 1 extends into the electrode housing 5, the return spring device 6 is compressed, and the electrical contact part contacts the annular resistor. The conductive post, the annular resistor, the electrical contact part, and the first and second parts of the electrode core rod form an electrical connection. When the second part of the electrode core rod continues to extend into the electrode housing, the electrical contact part disengages from the annular resistor, and the electrical connection between the electrode core rod and the conductive post is broken. Figure 2 As shown.

[0042] The electrode core rod 1 is made of a material with high thermal conductivity and high electrical conductivity to reduce Joule heat loss and improve the efficiency of electrical energy to heat energy conversion.

[0043] An insulating ring 2 is provided inside the electrode housing 5. The insulating ring 2 is located at the front end of the ring resistor 4. When the second part of the electrode core rod 1 extends into the electrode housing 5, the electrical contact part first contacts the insulating ring 2. When the second part of the electrode core rod 1 continues to extend in, the electrical contact part then contacts the ring resistor 4.

[0044] The power unit includes a hydraulic rod 201 and a hydraulic control system. The hydraulic rod 201 includes several hydraulic units arranged in sequence. When the hydraulic rod retracts, the hydraulic units are sequentially retracted into adjacent hydraulic units. The hydraulic rod is installed as a whole in the inner ring of the spring. One end of the hydraulic rod 201 is fixedly connected to the electrical contact part of the electrode core rod 1, and the other end is fixedly connected to the electrode housing 5. The electrode housing 5 is provided with inlet and outlet ports (port 1, port 2) corresponding to the inlet and outlet ports of the hydraulic rod 201. The hydraulic control system controls the extension and retraction of the hydraulic rod 201 by controlling the flow of liquid 202 from the inlet and outlet ports of the electrode housing 5.

[0045] Example 2

[0046] This embodiment of a plate forging fixture based on dynamic matching of form and heat includes an electrode head device 12, a mold, and an external circuit. The electrode head device 12 includes several upsetting heating electrodes as described in Embodiment 1. In this embodiment, the electrode head device 12 includes a substrate and several upsetting heating electrodes arranged in an array on the substrate. Specifically, it is equipped with 15 columns and 5 rows of aligned upsetting heating electrodes. The conductive post of each upsetting heating electrode can be connected in parallel to the power supply of an external circuit. The mold includes a support mold and a forming mold 10. The support mold is used to fix the billet 14. The forming mold is set on the forming surface of the billet and is used for forming the billet. The forming mold is provided with several through holes for the first part of the electrode core rod 1 to extend into. After the first part of the electrode core rod 1 extends into the through holes, it contacts the billet. The billet and the conductive post 3 of the upsetting heating electrode are connected to the external circuit. The length of the annular resistor 4 of each upsetting heating electrode is determined according to the distance from the initial plane of the billet to the forming surface of the forming mold. When the billet is completely attached to the forming mold, the electrical contact part of the electrode core rod 1 is separated from the annular resistor. The support mold includes a rear mold 11, a lower pad 8, and a lower pad support frame 9. The rear mold is used to install on the rear end of the blank; the lower pad is used to install on the lower surface end of the electrode head device; and the lower pad support frame is located on the upper part of the lower pad to support the electrode head device. The surface of the mold is coated with a second insulating layer 13, which is an insulating coating or an insulating sleeve.

[0047] The conductive post 3 is connected to the power supply of the external circuit. The current flows through the electrical contact part of the electrode core rod 1 and then through the electrode head device 12 before flowing out of the billet. As the upsetting process proceeds, the electrode core rod 1 moves backward along the electrode shell 5. The length of the current flowing through the ring resistor 4 gradually increases, and the corresponding current gradually decreases. When the upsetting process is completed, the electrode core rod reaches the limit position, and the current loop is completely disconnected.

[0048] The processed materials are those that are difficult to deform at room temperature, such as titanium alloys, aluminum alloys, and high-strength steel. The sheet thickness can be 40-150mm. If the initial shape of the sheet material being processed and bent is plate-shaped, the height-to-width ratio should be less than 2.5; if it is cylindrical, the height-to-diameter ratio should be less than 3. The contact surface between the electrode mandrel 1 and the blank can be adjusted according to the blank profile to achieve better contact heating effect. The internal resistance length of the upsetting heating electrode needs to be designed according to the distance from the blank to the forming surface. During processing, the part of the sheet material that first contacts the forming mold, the electrode mandrel, reaches its limit position first, and the contacting heating electrode is de-energized first. The electrical parameters of the electrode array are independently adjustable, and a programmable power supply can be set. Different currents can be set for the optimal forming temperature of parts of different thicknesses and materials.

[0049] A thermocouple is embedded in the first part of the electrode core rod 1. The thermocouple is used to provide real-time feedback on the temperature of the interface between the electrode core rod 1 and the billet. The thermocouple (sensor) is connected to the PID closed-loop control system to prevent excessive local temperature from affecting the surface quality of the billet.

[0050] Example 3

[0051] In this embodiment, a plate forging process using the plate forging fixture based on dynamic matching of form and heat described in Embodiment 2 is employed. During upsetting, finite element analysis is first performed to identify areas with poor plasticity during the forming process. Combined with the actual processing temperature, the appropriate voltage magnitude and the required energizing time for each local area are determined based on the temperature rise formula and the temperature-equivalent plastic strain mapping model. The specific steps are as follows:

[0052] Step 1: Determine the blank parameters and target workpiece parameters, and obtain the forming die parameters;

[0053] Step 2: Perform simulation design based on the forming mold parameters, blank parameters and target workpiece parameters to obtain the annular resistance length of each upsetting heating electrode and the processing control parameters;

[0054] Step 3: Based on the forming die parameters and the annular resistance length of each upsetting heating electrode, obtain the die and electrode head device, and install the blank, die, electrode head device and external circuit.

[0055] Step 4: Start the hydraulic press for upsetting and set the processing parameters according to the processing control parameters;

[0056] Step 5: As the upsetting process proceeds, the electrode mandrel moves backward along the electrode shell. The length of the current flowing through the annular resistor gradually increases, and the corresponding current gradually decreases. When the hydraulic head of the hydraulic press reaches a distance threshold close to the electrode mandrel, the control power device retracts the electrode mandrel to avoid damaging it. Specifically, the hydraulic rod is controlled to retract, causing the electrode mandrel to retract. During processing, the hydraulic rod in the electrode head device that has not retracted does not dampen the retraction of the electrode mandrel. When the billet at the upsetting heating electrode contact portion adheres to the forming mold, the electrical contact portion of the electrode mandrel disengages from the annular resistor, and the current circuit is broken. After the hydraulic head presses down, all electrode heads covered by the lower end face of the hydraulic head during its movement are in a de-energized state. That is, all electrode mandrels pressed against by the hydraulic head retract, de-energizing the electrode mandrel.

[0057] Step 6: Repeat step 5 until the processing is complete.

[0058] like Figure 4 As shown, the simulation design process includes the following steps:

[0059] Step 21: Based on the billet parameters and target workpiece parameters, simulate the entire bending-upsetting process using Abaqus / Explicit finite element simulation software. Extract the equivalent plastic strain (PEEQ) field distribution and workpiece deformation field data from the post-processing module of the finite element simulation software. Determine the threshold θ of the equivalent plastic strain based on the billet parameters. Based on the threshold, determine the high-strain and low-strain regions of the billet using the calculation module. The high-strain region is the area where PEEQ > θ, usually located on the outer side of the bend and the upsetting bulge. The low-strain region is the area where PEEQ < θ, mostly existing in the core of the workpiece and areas with insufficient deformation.

[0060] The spatial distribution of the plastic strain field (PEEQ) reflects the material's flow characteristics. In the manufacturing process, high PEEQ regions require heating to soften the material and reduce deformation resistance, thereby suppressing work hardening, surface cracking, and internal damage. Low PEEQ regions, on the other hand, require precise temperature control to balance deformation adequacy and flow stability. Transforming real-time PEEQ distribution into an effective heating control strategy allows for matching local temperature field regulation with the material's deformation state, resulting in a dual improvement in energy consumption control and forming quality.

[0061] Step 22: Obtain the strain gradient during billet forming based on the equivalent plastic strain field distribution. Using a mapping model between the temperature field and the equivalent plastic strain gradient (the mapping model parameters can be obtained through conventional thermal simulation experiments), generate a target temperature distribution function based on the amplitude of the strain gradient, and convert the strain gradient during billet forming into a temperature control command.

[0062] The temperature-equivalent plastic strain mapping model is as follows: , The target forming temperature, This refers to the recrystallization temperature of the billet (e.g., 650℃ for steel). and These are material-related constants. The strain rate factor, The spatial gradient of the equivalent plastic strain.

[0063] For high gradient regions ( >θ) Implement enhanced heating measures: increase the density of energized electrodes and increase the current amplitude to achieve localized thermoforming in the experiment; for low gradient regions ( <θ) The heat preservation control mode is adopted: the number of working electrodes is reduced and the current amplitude can be appropriately reduced to achieve precise spatial distribution of energy.

[0064] Step 23: Based on the target forming temperature of different areas of the billet A process parameter table containing the coordinates of each upsetting heating electrode, the current amplitude of each upsetting heating electrode, and the energizing heating time is generated using the temperature rise calculation formula; the temperature rise calculation formula is: In the formula, ΔT is the temperature rise of the billet. For current density, The resistivity of the material The duration of the applied current, For specific heat capacity, This represents the material density.

[0065] Step 24: Perform the thermo-mechanical coupling verification process. Construct an electrothermal-structural multiphysics model in the finite element simulation software Abaqus: import the electrode layout parameters from the process parameter table, simulate the Joule heating effect, rerun the simulation of bending-upsetting process, and collect new equivalent plastic strain PEEQ field data to calculate the PEEQ standard deviation σ and the maximum mold gap value.

[0066] Step 25: Perform uniformity compliance judgment: When the standard deviation of equivalent plastic strain σ meets the uniformity requirements and the maximum mold gap is compliant, the process is judged to be compliant and the final process parameter table is output; if the process is not compliant, return to step 22 and perform iterative optimization with the new equivalent plastic strain field distribution as input until the process is compliant.

[0067] like Figure 5 As shown, in this embodiment, a solid long plate made of TC4 material is processed by cutting and bending the middle part to obtain a plate with a thickness of 40mm, a width of 150mm, and a height of 300mm. The plate is then upset. Due to the difficulty of processing TC4 material at room temperature using traditional upset processing, a large forming force is required. If an external energy field is applied to process the entire part, a temperature field needs to be applied to a large area, resulting in a large energy margin. For the poor local plastic flow, electric assisted forming is used to induce local stress relaxation, specifically by heating the poor plastic parts.

[0068] First, based on the simulation design of the corresponding workpiece and its corresponding processing parameters, the material parameters are input (in this embodiment, the density of material TC4). Specific heat capacity resistivity recrystallization temperature The upsetting simulation was performed on the sample to obtain the PEEQ field distribution and deformation field data. After processing in Abaqus, the spatial gradient of the PEEQ field was calculated. Average strain in high strain zone Low strain zone average Substituting the values ​​into the mapping model, the final forming temperature is obtained. The forming temperatures in the high-strain and low-strain regions are then derived. Using the temperature rise formula, the energizing time can be calculated. Based on the mapping model, the temperature of the high-temperature deformation zone is 900℃, and the temperature of the low-temperature deformation zone is 880℃. According to the temperature rise formula, the energizing time in the high-deformation zone is 482 seconds, and the energizing time in the low-deformation zone is approximately 2942 seconds. Based on the electrode contact area... (Electrode tip φ50mm), current I Therefore, the required current magnitude is obtained.

[0069] The required length of the internal annular resistor of the heating electrode is designed based on the length of the sheet metal and the forming surface. The initial sheet metal is a plate-shaped part that is approximately rectangular. The distance between the front end face of the plate-shaped part and the curved surface of the forming mold should be greater than the limit of the retraction distance of the corresponding electrode core rod. The internal annular resistor length corresponding to the row of electrode heads with the shortest distance between the front end face of the plate-shaped part and the forming mold is also the shortest. During the processing, the heating electrode head is de-energized first at the part where the blank and the forming mold first adhere. For the remaining unadheded parts, the electrode head still provides a certain current. As the retraction distance of the electrode core rod gradually increases, the current gradually decreases. After complete adhesion, the heating electrode head is completely de-energized.

[0070] The next step is to install the mold. First, fix the rear mold to the rear end of the plate, install the lower pad and support frame, and finally install the forming mold and heating electrodes. Adjust the coaxiality, and connect the power supply to the heating electrodes. Figure 6 and Figure 7 As shown. The platen is fixed to the hydraulic press base. Once the fixed mold equipment is installed, the programmable power supply is turned on, outputting current according to the process parameter table, starting the hydraulic press, and executing bending-upsetting forming according to the preset program. During the forming process, the hydraulic press lowers the hydraulic head. When the distance between the hydraulic head and the nearest electrode mandrel reaches the distance threshold, the entire row of electrode mandrels that is at the distance threshold retracts, causing the hydraulic rods in that row to contract, thus retracting the electrode mandrels. This step is repeated until processing is complete. During processing, the hydraulic rods in the electrode head device that do not retract do not dampen the contraction of the electrode mandrels. Simultaneously, it is set to pause the downward pressure of the hydraulic head when the oil pressure sensor in the main cylinder of the hydraulic press shows an abnormal reading. When initially contacting the blank, the oil pressure reading will tend to stabilize to a certain value. Afterward, if a large fluctuation occurs in the oil pressure curve during processing, it indicates an abnormality, and the pressure head is stopped to prevent damage to the electrode mandrels. Temperature is monitored in real time during the process, and the current is finely adjusted through a PID system to maintain temperature stability. During the forming process, the electrode mandrel initially generates heat by energizing the entire billet. As upsetting progresses, the initially planar portion deforms forward due to the extrusion pressure, such as... Figure 8As shown, during the process, the portion with good plasticity extends further than the portion with poor plasticity. The greater the retraction distance of the electrode core rod at the electrode head, the smaller the current generated in that section. The longer the current flows through the annular resistor in that section, the smaller the current flowing through that segment. Figure 9 The middle section shows the intermediate temperature diagram during the processing. The temperature distribution is shown in Table 1. When the electrode core is fully compressed, the current circuit is broken, and heating stops, as shown in Table 1. Figure 10 As shown, Figure 6 , 8 Point A in 10 represents the current inflow point of conductive post 3, point B represents the current outflow point of conductive post 3, point C represents the end point of the ring resistor 4 near the reset spring device 6, and point D represents the current inflow point of electrode core rod 1.

[0071] Table 1 Temperature Distribution

[0072]

[0073] The final machined parts were inspected using a 3D scanner. The maximum mold gap was 0.32mm, meeting the requirements. Metallographic microscopy revealed that the grain size difference between high-strain and low-strain regions was ≤15%, with a PEEQ standard deviation σ=0.04, satisfying the uniformity requirements. The traditional integral heating process (heating to 900℃) consumes approximately 120kWh, while this process consumes approximately 78kWh, representing a 35% reduction in energy consumption, achieving the expected goal.

Claims

1. A upsetting heating electrode based on dynamic matching of shape and heat, characterized in that, The electrode includes an electrode shell (5), an electrode core rod (1), a reset spring device (6), a ring resistor (4), a conductive column (3) and a power device, the inner wall of the electrode shell (5) is provided with the ring resistor, the electrode core rod (1) includes a first part and a second part which are fixedly connected in sequence, the end of the first part of the electrode core rod (1) is used for contacting a blank, the second part of the electrode core rod (1) extends into the electrode shell (5) and moves along the electrode shell (5), the outer periphery of the second part of the electrode core rod (1) is provided with an insulating layer, the end of the second part of the electrode core rod (1) is provided with an electric contact part used for electrically contacting the ring resistor of the inner wall of the electrode shell (5), the reset spring device and the power device are arranged between the electric contact part and the electrode shell (5), the power device is used for driving the electrode core rod to move along the electrode shell, the length of the electrode shell (5) is longer than the length of the second part of the electrode core rod (1), the electrode shell is provided with the conductive column (3), one end of the conductive column (3) is electrically connected with the ring resistor, the other end of the conductive column extends out of the electrode shell and is used for connecting an external circuit, when the second part of the electrode core rod (1) extends into the electrode shell (5), the reset spring device (6) is compressed, the electric contact part contacts the ring resistor, the conductive column, the ring resistor, the electric contact part and the first part and the second part of the electrode core rod form an electrical connection, when the second part of the electrode core rod continues to extend into the electrode shell, the electric contact part is separated from the ring resistor, and the electrical connection between the electrode core rod and the conductive column is disconnected.

2. The upsetting heating electrode based on shape thermodynamic matching according to claim 1, characterized in that, The electrode core rod (1) has a stepped structure with the first part having a larger outer diameter than the second part, and the outer diameter of the first part of the electrode core rod (1) is larger than the inner diameter of the electrode shell (5), so that the first part of the electrode core rod (1) cannot extend into the electrode shell (5).

3. The upsetting heating electrode based on shape thermodynamic matching according to claim 1, characterized in that, The electrode shell (5) is provided with an insulating ring (2) in the inner wall, and the insulating ring (2) is located in front of the ring resistor (4), so that when the second part of the electrode core rod (1) extends into the electrode shell (5), the electric contact part first contacts the insulating ring (2), and when the second part of the electrode core rod (1) continues to extend, the electric contact part contacts the ring resistor (4).

4. The upset heating electrode based on shape thermodynamic matching according to claim 1, wherein, The power device includes a hydraulic rod (201) and a hydraulic control system, one end of the hydraulic rod (201) is fixedly connected with the electric contact part of the electrode core rod (1), the other end of the hydraulic rod (201) is fixedly connected with the electrode shell (5), the electrode shell (5) is provided with an inlet and outlet, and the hydraulic control system controls the extension and retraction of the hydraulic rod (201) through the inlet and outlet of the electrode shell (5).

5. A plate forging tool based on shape-thermal dynamic matching, characterized in that, The electrode head device (12) includes a plurality of upsetting heating electrodes according to any one of claims 1 to 4, the mold includes a support mold for fixing the blank and a forming mold provided on the forming surface of the blank for forming the blank, the forming mold is provided with a plurality of through holes for the first part of the electrode core rod (1) to protrude, and the first part of the electrode core rod (1) is in contact with the blank after protruding through the through hole. The blank and the conductive column (3) of the upsetting heating electrode are connected to the external circuit, the length of the annular resistor (4) of each upsetting heating electrode is determined according to the distance from the initial plane of the blank to the forming surface of the forming mold, and when the blank completely fits the forming mold, the electrical contact part of the electrode core rod (1) is separated from the annular resistor.

6. The shape thermal dynamic matching based plate forging tooling of claim 5, wherein, The surface of the mold is coated with an insulating layer.

7. The shape dynamic matching based plate forging tooling of claim 6, wherein, The first part of the electrode core rod (1) is embedded with a thermocouple, which is used to feedback the temperature of the contact interface between the electrode core rod (1) and the blank in real time.

8. A plate forging process using the plate forging tooling based on shape-thermal dynamic matching of claim 5, characterized in that, The method comprises the following steps: Step 1: determining the blank parameters and target workpiece parameters, and obtaining the forming mold parameters; Step 2: simulating and designing according to the forming mold parameters, blank parameters and target workpiece parameters, obtaining the length of the annular resistor of each upsetting heating electrode and the processing process control parameters; Step 3: obtaining the mold and electrode head device according to the forming mold parameters and the length of the annular resistor of each upsetting heating electrode, and installing the blank, mold, electrode head device and external circuit; Step 4: starting the hydraulic machine to perform upsetting forming, and setting the processing parameters according to the processing process control parameters; Step 5: as the upsetting process proceeds, the electrode core rod moves backward along the electrode shell, the length of the annular resistor through which the current flows gradually increases, and the corresponding current gradually decreases; when the hydraulic head of the hydraulic machine reaches the distance threshold close to the electrode core rod, the power device is controlled to retract the electrode core rod reaching the distance threshold to avoid damaging the electrode core rod by the hydraulic head; when the blank of the contact part of the upsetting heating electrode fits the forming mold, the electrical contact part of the electrode core rod is separated from the annular resistor, and the current loop is disconnected; Step 6: repeating step 5 until the processing is completed.

9. The shape kinetic dynamic matching based plate forging process of claim 8, wherein, The simulation design process comprises the following steps: Step 21: simulating the whole process of bending-upsetting process by finite element simulation software according to the blank parameters and target workpiece parameters, extracting the equivalent plastic strain field distribution and workpiece deformation field data in the finite element simulation software; determining the threshold value of equivalent plastic strain according to the blank parameters, and determining the high strain zone and low strain zone of the blank based on the threshold value; Step 22: obtaining the strain gradient in the blank forming process according to the equivalent plastic strain field distribution, generating a target temperature distribution function according to the amplitude of the strain gradient through a mapping model of temperature field and equivalent plastic strain gradient, and converting the strain gradient in the blank forming process into temperature control instructions: Step 23: generating a process parameter table containing the coordinates of each upsetting heating electrode, the current amplitude of each upsetting heating electrode and the current heating time according to the target forming temperature of different regions of the blank through a temperature rise calculation formula; Step 24: Perform a thermal-mechanical coupling verification process, build an electro-thermal-structural multi-physical field model in finite element simulation software: import the parameters in the process parameter table, simulate the Joule heating effect, re-run the simulation of the bending-upsetting process, collect new equivalent plastic strain field data, calculate the full-field equivalent plastic strain standard deviation and the maximum gap value between the die and the workpiece; Step 25: Implement uniformity compliance judgment: when the equivalent plastic strain standard deviation meets the uniformity requirement and the maximum gap between the die and the workpiece is compliant, it is determined that the process is compliant, and the final process parameter table is output; if the process is not compliant, return to step 22, and iterate optimization with the new equivalent plastic strain field distribution as input until the process is compliant.

10. The shape thermodynamic dynamic matching based plate forging process of claim 8, wherein, The blank is a difficult-to-deform material at room temperature, including titanium alloy, aluminum alloy, and high-strength steel.

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