An electro-assisted forming device and process for a grooved annular plate

Abstract

The present invention discloses an electro-assisted forming device and process for a grooved annular plate member. The electro-assisted forming device includes a lower die and an upper die fixedly arranged directly above the lower die. At least one row of nitrogen gas springs is fixedly arranged on both sides of the bottom of the upper die. A wavy stamping forming groove is formed on the top surface of the lower die. A stamping punch matching the stamping forming groove is fixedly arranged at the bottom of the upper die. A plurality of electrode bars are fixedly arranged on the surface of the stamping punch along the length direction. A liftable pre-pressing plate is movably sleeved outside the stamping punch. A first electrode plate and a second electrode plate located on both sides of the stamping punch respectively are arranged on the bottom surface of the pre-pressing plate. The present invention can stamp out a wavy grooved thin plate member at one time, and then cut it to form a plurality of grooved sector thin plate members with the same specifications, so as to be spliced to form a grooved annular plate member; by adopting a method of sectional power supply, the stamping forming of the final part is comprehensively realized, and the forming work efficiency and the uniformity of each area are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal stamping forming, and specifically to an electro-assisted forming device and process for a grooved annular plate Background Art

[0002] An aircraft includes a spacecraft, a carrier vehicle, and an upper stage. The upper stage is the last stage or a multi-stage rocket independent of the basic stage in a multi-stage carrier rocket. The upper stage of a carrier rocket is a key structure in aerospace technology, which poses an extremely urgent need for the development and production of large-size or extra-large-size annular tanks with a large capacity. There are three key technical challenges in the high-precision forming of an annular tank: First, the shape is extremely complex, including large sizes and small features, as well as complex features such as significantly different curvatures, special-shaped closed cross-sections, extra-large feature sizes, and ultra-thin wall thicknesses. These features make the deformation amount of the blank far exceed the limit value formed by traditional process defects. Second, the material is a difficult-to-deform alloy, and titanium alloy has poor room-temperature forming performance and high yield strength. Third, dimensional accuracy and strong plasticity matching are required. Since the annular tank cannot be reprocessed after forming due to its ultra-thin characteristics, the forming accuracy must be ensured through direct forming. The challenges of the above key technologies are coupled and superimposed on each other, making the manufacturing of components extremely difficult. The existing forming technology based on a rigid die cannot form such complex integral structures due to the limitation of the loading space. Therefore, such components are often decomposed into small-size components with simple shapes (usually equal fan shapes), and then welded into an integral annular component after forming.

[0003] The following deficiencies exist in traditional hot forming processes: The equipment for traditional hot forming mainly includes a heating furnace and a press. It is difficult to transport large-size annular tanks, and warping and heat dissipation occur during transportation. The heat dissipation temperature drop within 1 minute is as high as 300°C, so the heat energy consumption of the sheet material is large. When the ultra-thin sheet at 800°C comes into contact with the cold die at 20°C, heat is conducted from the high-temperature object to the low-temperature object, and the temperature of the ultra-thin sheet drops quickly, the fluidity of the material decreases, and the forming quality is poor. To solve the problem of the temperature drop during forming, it is necessary to increase the preheating temperature of the ultra-thin sheet. However, the higher the temperature, the stronger the oxidation degree of the titanium alloy. The long-term high temperature causes the titanium alloy to be oxidized, making the ultra-thin sheet prone to hydrogen embrittlement during the forming process. The ultra-thin sheet has to experience a long-term high-temperature environment in the heating furnace and still needs to be kept warm for a period of time after being heated to the preset temperature, and the internal tissue properties of the material change, showing a large difference from the original tissue, sacrificing the tissue properties in exchange for the forming of components. There is an obvious springback phenomenon during the stamping process of the ultra-thin sheet, and subsequent heat treatment experiments are also required to achieve the purpose of stress relaxation.

[0004] At the same time, during the separate forming process of large-size components, due to the inconsistent curvature sizes on the inner and outer sides, stress imbalance is likely to occur, resulting in premature fracture, and the rejection rate is relatively high. Summary of the Invention

[0005] In view of the above defects and deficiencies, the present invention provides an electro-assisted forming device and process for a grooved annular plate member. By providing a wavy stamping forming groove and a matching stamping punch, a wavy grooved thin plate member can be stamped out at one time, and then cut into multiple grooved sector thin plate members with the same specifications, so that a grooved annular plate member can be spliced; by designing a flange area and a cavity area for the blank, applying a blank holding force to the flange area and applying a part forming punching force to the cavity area, and adopting a method of adding electricity in zones to comprehensively realize the stamping forming of the final part, the forming work efficiency and the uniformity of each area are improved.

[0006] To solve the above technical problems, a technical solution adopted by the present invention is:

[0007] An electro-assisted forming device for a grooved annular thin plate member, comprising a lower die fixedly arranged on the top surface of a stamping workbench, and an upper die fixedly arranged on the bottom surface of a stamping lifting table and located directly above the lower die. At least one row of nitrogen gas springs is fixedly arranged on both sides of the bottom of the upper die. A wavy stamping forming groove is formed on the top surface of the lower die. A stamping punch matching the stamping forming groove is fixedly arranged on the bottom of the upper die. A plurality of electrode bars are fixedly arranged on the surface of the stamping punch along the length direction. A liftable pre-pressure plate is movably sleeved outside the stamping punch. A first electrode plate and a second electrode plate are arranged on the bottom surface of the pre-pressure plate and located on both sides of the stamping punch respectively;

[0008] Before the stamping punch stamps the blank to cause bending deformation, the first electrode plate and the second electrode plate are simultaneously in contact with both sides of the surface of the blank. The two electrode plates have opposite electricities, and a high-frequency pulsed current is passed into the blank for a preset duration; during the process of the stamping punch stamping the blank to cause bending deformation, the two electrode plates have the same electricity and are opposite to the electricity of the electrode bars, and the surface of the blank sequentially contacts the electrode bars from the center to both sides to pass a high-frequency pulsed current into the blank for a corresponding preset duration; when holding pressure after the stamping punch finishes stamping, the two electrode plates have opposite electricities, and a low-frequency pulsed current is passed into the blank for a preset time.

[0009] Further, the stiffness coefficients of two adjacent nitrogen gas springs are different and the free end lengths are the same, or the stiffness coefficients of two adjacent nitrogen gas springs are the same and the free end lengths are different.

[0010] Further, spring mounting seats are fixedly connected to both sides of the bottom surface of the upper die. Spring embedding grooves are formed on the bottom surfaces of the spring mounting seats. The nitrogen gas springs are fixedly embedded in the spring embedding grooves, and the free ends of the nitrogen gas springs movably penetrate below the bottom surfaces of the first electrode plate and the second electrode plate.

[0011] Further, a punch mounting seat located between two spring mounting seats is fixedly connected to the middle of the bottom surface of the upper die. The stamping punch is fixedly connected to the bottom surface of the punch mounting seat. A square through hole located directly below the punch mounting seat is formed in the pre-pressure plate.

[0012] Further, lifting bolts are respectively fixedly connected to both sides of the top surface of the pre-pressure plate. The lifting bolts are movably arranged in the spring mounting seats.

[0013] Further, electrode plate embedding grooves are respectively formed on both sides of the bottom surface of the pre-pressure plate. The first electrode plate and the second electrode plate are respectively embedded in the corresponding electrode plate embedding grooves. The bottom surfaces of the first electrode plate and the second electrode plate are located on the same horizontal plane and protrude from the bottom surface of the pre-pressure plate.

[0014] Further, a plurality of terminal embedding grooves are formed in the outer side surfaces of the first electrode plate and the second electrode plate. Wiring terminals are arranged in the terminal embedding grooves.

[0015] Further, a high-silica fiber cloth is laid on the surface of the stamping forming groove.

[0016] There is also provided an electro-assisted forming process for a grooved annular thin plate member, which is applied to the electro-assisted forming device for a grooved annular thin plate member as described above, and includes the following steps:

[0017] S1. Place the blank to be formed on the top surface of the lower die and adjust the position of the blank.

[0018] S2. The stamping lifting table drives the upper die, the nitrogen spring, the stamping punch, the pre-pressure plate, the first electrode plate and the second electrode plate to move downward synchronously. The first electrode plate and the second electrode plate continue to move downward until they simultaneously contact the top surface of the blank.

[0019] S3. The free ends of the nitrogen springs contact both sides of the top surface of the blank and tightly press the blank on the top surface of the lower die.

[0020] S4. The first electrode plate and the second electrode plate are energized with opposite polarities, and a high-frequency pulsed current is passed into the blank for a preset time.

[0021] S5. The electrode bars are energized. The first electrode plate and the second electrode plate are energized with the same polarity and have the opposite polarity to that of the electrode bars.

[0022] S6. The stamping punch continues to move downward. After contacting the top surface of the blank, the blank is bent and deformed so that its surface contacts the electrode bars from the inside out. A high-frequency pulsed current is passed into the blank. After each electrode bar is energized for a corresponding preset duration, it is powered off.

[0023] S7. After the stamping punch descends to the lowest position, it holds the pressure for a preset duration. The first electrode plate and the second electrode plate are energized with opposite polarities, and a low-frequency pulsed current is passed into the slab for a preset time.

[0024] S8. The first electrode plate and the second electrode plate are de-energized. The stamping lifting table drives the upper die to ascend and reset. After the stamping part cools down, it is taken out from the lower die.

[0025] S9. The surplus materials on each side of the stamping part are removed to obtain a wavy linear groove-shaped thin plate part, and then it is cut to form a groove-shaped fan-shaped thin plate part.

[0026] S10. The fan-shaped groove-shaped thin plate parts are sequentially spliced and welded together to form a groove-shaped annular thin plate part.

[0027] Further, in step S3, the pressure values applied to the surface of the slab by the free ends of two adjacent nitrogen springs are different.

[0028] Further, in step S6, the magnitude of the current density passing through each electrode bar is inversely proportional to the thinning degree of the corresponding slab stretching area.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. By setting the wavy linear stamping forming groove and the matching stamping punch, the present invention can stamp out a wavy linear groove-shaped thin plate part at one time, and then cut it to form multiple groove-shaped fan-shaped thin plate parts with the same specifications, so as to splice and form a groove-shaped annular thin plate part, realizing the miniaturized production and manufacturing of large workpieces.

[0031] 2. Since the wavy linear groove-shaped thin plate part formed by stamping is integrally and continuously formed, that is, the large curvature forming area of each groove-shaped fan-shaped thin plate part is continuous with the small curvature forming area of the adjacent groove-shaped fan-shaped thin plate part, the forming performance of each part inside and outside the groove-shaped fan-shaped thin plate part after cutting can be guaranteed to be the same, thus significantly improving the overall quality of the groove-shaped annular thin plate part formed after welding.

[0032] 3. The forming device of the present invention designs a flange area and a cavity area for the slab, provides a blank holding force for the flange area and a part forming punching force for the cavity area, and comprehensively realizes the stamping forming of the final part by means of zoning power-on, improving the forming work efficiency and the uniformity of forming in each area. By passing high-frequency pulsed currents with different current densities into different forming areas of the slab to achieve electro-assisted heating, the phenomenon that the material in a local area becomes overly thin and the local temperature is too high after the mold is closed can be avoided, achieving the effect of relatively uniform overall temperature of the material and effectively reducing the risk of the thin area being broken through by high pulsed currents.

[0033] 4. The present invention realizes the rapid heating of the slab by means of electrically assisted heating, which can effectively improve the heating efficiency of the slab, avoid the slab being in the heating state for a long time, and prevent the grain coarsening and property deterioration of the internal structure of the material. As a result, the surface forming quality of the semi-finished part is better. After stamping forming, the overall stress relaxation is achieved through electric heating, the residual stress decreases rapidly, and the springback amount is reduced, making the forming part have high surface accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 One of the three-dimensional structural schematic diagrams of the electric-assisted forming device of the present invention;

[0035] Figure 2 Two of the three-dimensional structural schematic diagrams of the electric-assisted forming device of the present invention;

[0036] Figure 3 One of the three-dimensional structural schematic diagrams of the upper die and its various components;

[0037] Figure 4 Two of the three-dimensional structural schematic diagrams of the upper die and its various components;

[0038] Figure 5 One of the three-dimensional structural schematic diagrams of the assembled state of two electrode plates on the pre-pressing plate;

[0039] Figure 6 Two of the three-dimensional structural schematic diagrams of the assembled state of two electrode plates on the pre-pressing plate;

[0040] Figure 7 Three-dimensional structural schematic diagram of the distribution state of the wiring terminals in the electrode plate;

[0041] Figure 8 Three-dimensional structural schematic diagram of the stamping punch and the electrode bar;

[0042] Figure 9 Three-dimensional structural schematic diagram of the lower die;

[0043] Figure 10 Schematic diagram of the pressing state of the slab on the lower die;

[0044] Figure 11 Three-dimensional structural schematic diagram of the wavy linear groove-shaped thin plate part prepared by the present invention;

[0045] Figure 12 Cutting position schematic diagram of cutting the wavy linear groove-shaped thin plate part into a groove-shaped sector thin plate part;

[0046] Figure 13 Three-dimensional structural schematic diagram of the groove-shaped sector thin plate part prepared by the present invention;

[0047] Figure 14Schematic three-dimensional structure diagram of the grooved annular thin plate part prepared according to the present invention.

[0048] In the figure: 1, lower die; 101, stamping forming groove; 2, upper die; 3, stamping punch; 4, electrode bar; 5, pre-pressing plate; 501, limiting counterbore; 502, positioning post; 503, square through-hole; 504, threaded connection hole; 6, first electrode plate; 601, terminal embedding groove; 7, second electrode plate; 8, nitrogen spring; 9, spring mounting seat; 10, punch mounting seat; 11, lifting bolt; 12, wiring terminal; 100, stamping workbench; 200, stamping lifting table. Detailed implementation manners

[0049] The following will elaborate on the preferred embodiments of the present invention in conjunction with the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0050] It should be noted that when a component is referred to as being "installed on" another component, it can be directly on the other component or there may also be an intermediate component. When a component is considered to be "set on" another component, it can be directly set on the other component or there may be an intermediate component at the same time. When a component is considered to be "fixed to" another component, it can be directly fixed to the other component or there may be an intermediate component at the same time.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "or / and" used herein includes any and all combinations of one or more of the related listed items.

[0052] The present invention provides an electro-assisted forming device for grooved annular thin plate parts, which is used to prepare a Figure 11 wavy grooved thin plate part as shown, and then the wavy grooved thin plate part is cut along the cutting position shown by the dotted line in Figure 12 to form a grooved sector thin plate part as shown in Figure 13 , and then the grooved sector thin plate parts are spliced and welded to form a grooved annular thin plate part as shown in Figure 14 . When the electro-assisted forming device is actually used, it cooperates with existing stamping forming equipment, high-voltage pulse generators and circuit switching control systems to achieve power supply and control. The logic control of current supply and line switching are all prior arts and will not be elaborated herein.

[0053] Please refer to Figures 1 to 10, the electro-assisted forming device includes a lower die 1 fixedly arranged on the top surface of the stamping workbench 100, and an upper die 2 fixedly arranged on the bottom surface of the stamping lifting table 200 and located directly above the lower die 1. The upper die 2 and its various components are driven up and down by the stamping lifting table 200 to complete the die closing and die opening processes of the upper and lower dies. As Figure 9 shown, a wave-shaped stamping forming groove 101 is formed on the top surface of the lower die 1. The stamping forming groove 101 is a curved groove with a semi-circular cross-section and a wave path. The wave path is an arc line with continuous curvature and the same radius, that is, the offset distances from the top two edges of the stamping forming groove to the wave path are equal. In the attached drawings of this embodiment, taking the example that a single wave-shaped grooved thin plate can be cut into two grooved sector thin plates for illustration.

[0054] A stamping punch 3 matching the stamping forming groove 101 is fixedly arranged at the bottom of the upper die 2. Specifically, a punch mounting seat 10 is fixedly connected to the middle of the bottom surface of the upper die 2 by bolts, and the stamping punch 3 is fixedly connected to the bottom surface of the punch mounting seat 10 by bolts, so that the stamping punch 3 and the upper die 2 are rigidly connected, thereby providing power for the downward movement of the stamping punch 3 and the bending deformation of the slab. By setting the wave-shaped stamping forming groove and the matching stamping punch 3, a wave-shaped grooved thin plate can be stamped out at one time, and then cut into multiple grooved sector thin plates with the same specifications, so as to be spliced into a grooved annular thin plate, realizing the miniaturized production and manufacturing of large workpiece components.

[0055] A liftable pre-pressure plate 5 is movably sleeved outside the stamping punch 3, and a first electrode plate 6 and a second electrode plate 7 are arranged on the bottom surface of the pre-pressure plate 5 and located on both sides of the stamping punch 3 respectively. Specifically, lifting bolts 11 are threadedly connected to both sides of the top surface of the pre-pressure plate 5, and the smooth rod portions of the lifting bolts 11 movably penetrate through the spring mounting seats 9. The lifting bolts 11 are dowel screws, and sleeves are sleeved on their screw rod portions. Threaded connection holes 504 are formed in the top surface of the pre-pressure plate 5, and the threaded ends of the lifting bolts 11 are threadedly connected into the threaded connection holes 504; vertical counterbores are formed inside the spring mounting seats 9, and the sleeves are located in the small-diameter holes of the counterbores; through holes with the same diameter as the large-diameter holes of the counterbores are formed in the top surface of the upper die 2, and the nut portions of the lifting bolts 11 movably lift in the through holes and the large-diameter holes of the counterbores. In the free state without mold clamping, the pre-pressure plate 5 is located at the lowest vertical position and below the lowest end of the stamping punch 3. After the slab is accurately placed at the forming position on the top surface of the lower die 1, during the downward movement of the upper die 2, the bottom surfaces of the first electrode plate 6 and the second electrode plate 7 first come into contact with both sides of the top surface of the slab simultaneously. During the process of the upper die 2 driving the stamping punch 3 to continue moving downward, the lifting bolts 11 move upward relative to the spring mounting seats 9, and the pre-pressure plate 5 presses on the first electrode plate 6 and the second electrode plate 7 by its own gravity, enabling the first electrode plate 6 and the second electrode plate 7 to be in reliable contact with the top surface of the slab, and realizing pre-clamping of the forming positions on both sides of the top surface of the slab.

[0056] At least one row of nitrogen gas springs 8 are fixedly arranged on both sides of the bottom of the upper die 2 respectively. Specifically, spring mounting seats 9 located on both sides of the punch mounting seat 10 are fixedly connected to both sides of the bottom surface of the upper die 2 through bolts. Spring embedding grooves are formed in the bottom surfaces of the spring mounting seats 9, and the nitrogen gas springs 8 are fixedly embedded in the spring embedding grooves, which is convenient for pre-fixing each nitrogen gas spring 8 on the spring mounting seat 9 according to the preset arrangement order and then integrally fixing and assembling on the upper die 2.

[0057] After the first electrode plate 6 and the second electrode plate 7 pre-press the slab tightly, during the process of the upper die 2 continuing to move downward, the bottom output end of the nitrogen spring 8 penetrates through the pre-pressing plate 5 and contacts the top surface of the slab, and then applies a pressing force to the top surface of the slab through the force generated by its own compression, thereby tightly pressing the slab on the lower die 1. During the process of pressing the slab tightly, the nitrogen spring 8 also plays a buffering role in the die closing process between the upper die 2 and the lower die 1. Since the slab is rectangular in shape and the cavity area for stamping and forming is wavy, during the actual stamping and stretching process, the blank holding forces required for different curvature parts are different. Therefore, by actively distributing different blank holding forces to different curvature parts, this kind of non-uniformity can be utilized to achieve the uniform forming of thin-walled asymmetric special-shaped structures. Therefore, preferably, the stiffness coefficients of two adjacent nitrogen springs 8 are different and the free end lengths are the same, or the stiffness coefficients of two adjacent nitrogen springs 8 are the same and the free end lengths are different. In this embodiment, the first type of nitrogen spring 8 is selected. In this way, during the process of the upper die 2 driving each nitrogen spring 8 to move downward synchronously, for the nitrogen springs of the first distribution type, the free ends of each nitrogen spring 8 contact the surface of the slab at the same time, and then the free ends of each nitrogen spring 8 are compressed by the same distance. Due to the different stiffness coefficients, the local blank holding forces finally acting on the surface of the slab are also different; for the nitrogen springs of the second distribution type, the nitrogen spring with a longer free end length contacts the surface of the slab first, and the nitrogen spring with a shorter free end length contacts the surface of the slab later, and then the compression lengths of the free ends of each nitrogen spring 8 are different. Due to the same stiffness coefficient, the local blank holding forces finally acting on the surface of the slab are also different.

[0058] On both sides of the bottom surface of the pre-pressing plate 5, electrode plate embedding grooves are respectively opened. The first electrode plate 6 and the second electrode plate 7 are respectively embedded in the corresponding electrode plate embedding grooves and are fixedly connected by bolts. Further, positioning columns 502 are fixedly arranged in the electrode plate embedding grooves. Positioning holes are opened in both the first electrode plate 6 and the second electrode plate 7. Through the cooperation of the positioning holes and the positioning columns 502, the first electrode plate 6 and the second electrode plate 7 can be quickly and accurately positioned in the electrode plate embedding grooves. At the same time, the bottom surfaces of the first electrode plate 6 and the second electrode plate 7 are located in the same horizontal plane and protrude from the bottom surface of the pre-pressing plate 5, so as to ensure that both the first electrode plate 6 and the second electrode plate 7 are in reliable contact with the top surface of the slab.

[0059] A square through-hole 503 is provided in the pre-pressing plate 5 directly below the punch mounting seat 10. During the process of the upper die 2 driving the punching punch 3 to continue descending, the punching punch 3 and the punch mounting seat 10 can penetrate through the square through-hole to complete the subsequent stamping and forming process. A limiting sunk hole 501 is provided on the top surface of the pre-pressing plate 5 directly below the nitrogen spring 8 and on one side of the square through-hole 503. The major diameter of the limiting sunk hole 501 is not less than the outer diameter of the bottom end of the main body of the nitrogen spring 8, so that the bottom end of the main body of the nitrogen spring 8 can be smoothly embedded into the sunk hole 501. The minor diameter of the limiting sunk hole 501 is between the outer diameter of the bottom end of the main body of the nitrogen spring 8 and the outer diameter of the free end, to ensure that the free end of the nitrogen spring 8 can smoothly penetrate through the pre-pressing plate 5. After the bottom surfaces of the first electrode plate 6 and the second electrode plate 7 come into contact with the top surface of the blank, during the process of the nitrogen spring 8 and the spring mounting seat 9 moving downward following the upper die 2, the bottom end of the main body of the nitrogen spring 8 gradually approaches the top surface of the pre-pressing plate 5. When the punching punch 3 descends to the lowest position, the bottom end of the main body of the nitrogen spring 8 is above the top surface of the pre-pressing plate 5, or extends into the limiting sunk hole 501 and is above the groove bottom surface of the limiting sunk hole 501, that is, to ensure that there is no rigid contact between the bottom end of the main body of the nitrogen spring 8 and the pre-pressing plate 5, so that the pre-pressing plate 5, the first electrode plate 6 and the second electrode plate 7 will not cause movement interference to the blank holding effect between the nitrogen spring 8 and the blank.

[0060] After the first electrode plate 6 and the second electrode plate 7 are both in contact with the top surface of the blank and before the bottom end of the punching punch 3 contacts the top surface of the blank, the first electrode plate 6 and the second electrode plate 7 are respectively connected to the positive and negative output terminals of the high-frequency pulse generator, that is, the electrical properties of the first electrode plate 6 and the second electrode plate 7 are opposite, so as to pass a high-frequency pulse current through the blank for a preset duration (the specific duration is determined according to the appropriate stamping and forming temperature of the blank and the current density of the high-frequency pulse current), and the blank can be rapidly heated as a whole, so that the blank is at an appropriate deformation temperature. By adopting the method of electric heating assistance to realize the rapid heating of the blank, the heating efficiency of the blank can be effectively improved, the blank can be prevented from being in the heating state for a long time, and the grain coarsening and performance deterioration of the internal structure of the material can be avoided, so that the surface forming quality of the semi-finished part is better.

[0061] To improve the uniformity of the current density distribution in the first electrode plate 6 and the second electrode plate 7, a number of (3 in this embodiment as shown in Figure 7 ) terminal embedding grooves 601 are provided in the outer side surfaces of the first electrode plate 6 and the second electrode plate 7. Wiring terminals 12 are arranged in the terminal embedding grooves 601 and are fixed in the terminal embedding grooves 601 by bolts. By synchronously introducing pulse currents with the same parameters through a plurality of wiring terminals 12, the large difference in the current density loaded on the top surface of the blank in different regions caused by the self-resistance of the first electrode plate 6 and the second electrode plate 7 can be avoided.

[0062] A plurality of electrode bars 4 are fixedly arranged on the surface of the stamping punch 3 along the length direction. As Figure 4 and Figure 8 shown, in this embodiment, the number of the electrode bars 4 is 5, and they are evenly distributed at equal intervals along the semi-circular arc contour of the cross-section of the stamping punch 3. An electrode bar groove is formed on the surface of the stamping punch 3 along its length direction, and the electrode bars 4 are respectively and fixedly embedded in the electrode bar grooves to prevent the electrode bars 4 from changing positions during the stamping forming process, and the surfaces of the electrode bars 4 protrude parallel to the surface of the stamping punch 3, and the protruding height is such that the electrode bars 4 can reliably contact the surface of the slab and do not affect the bending forming process of the slab.

[0063] After the first electrode plate 6 and the second electrode plate 7 finish heating the slab, the first electrode plate 6 and the second electrode plate 7 are connected to the negative output terminal of the high-frequency pulse generator, and the electrode bars 4 are connected to the positive output terminal of the high-frequency pulse generator, that is, the first electrode plate 6 and the second electrode plate 7 have the same electric property and are opposite to the electric property of the electrode bars 4. The stamping punch 3 continues to move downward and starts to contact the center of the top surface of the slab, applying a stamping forming force to the slab to cause the slab to start bending deformation; at the same time, the lowermost electrode bar 4 (located at Figure 8 the middlemost position shown in

[0064] During the continuous bending deformation of the slab, the forming areas on both sides gradually bend upward and come into contact with the two side surfaces at the bottom of the stamping punch 3, so that the two electrode bars 4 on both sides above the electrode bar 4 at the bottom on the surface of the stamping punch 3 are respectively in contact with the surfaces of the forming areas on both sides of the slab (at this time, the electrode bar 4 at the bottom is in a power-off state). Then, they cooperate with the first electrode plate 6 and the second electrode plate 7 respectively to pass high-frequency pulsed current into the two side areas of the slab for a corresponding preset duration, so as to quickly heat the forming area of the slab, make up for the heat loss, and keep the forming area within a suitable deformation temperature range. During this process, since the middle part of the slab has been stretched and deformed and bent first, resulting in local material thickness reduction, if the power is continuously supplied for heating, problems such as excessive thinning leading to too high local temperature and even breakdown and fracture are likely to occur. Therefore, the electrode bar 4 at the bottom is in a power-off state. Also, since the heat loss rate of the slab from the central position to both sides gradually increases, by sequentially replacing the power supply of the outer electrode bars 4, the heating energy supplement of the two outer bending forming areas of the sheet material can be realized, and the heat supply to the formed part between the two forming areas can be stopped, so that the formed part reduces the forming performance and avoids further thinning due to subsequent tensile deformation. Moreover, since the drawing and thinning amounts of different deformation areas are different, the high-frequency current densities of different deformation areas should be different. The magnitude of the current density passed into each electrode bar 4 is inversely proportional to the thinning degree of the corresponding tensile area of the slab (the stamping speed can be considered constant, that is, the preset heating time of each electrode bar 4 can be considered the same), to avoid the phenomenon that the material in the local area is excessively thinned after the mold is closed, resulting in too high local temperature. The two electrode bars 4 at the top on both sides of the surface of the stamping punch 3 use the same method to quickly heat the forming area during the bending deformation of the slab (at this time, the three electrode bars 4 on the inner side are all in a power-off state). By passing high-frequency pulsed current with different current densities into different forming areas of the slab for electro-assisted heating, the phenomenon that the material in the local area is excessively thinned after the mold is closed, resulting in too high local temperature, can be avoided, achieving the effect of relatively uniform overall temperature of the material and effectively reducing the risk of the thin area being broken down by the high pulsed current.

[0065] Preferably, a high-silica fiber cloth is laid on the surface of the stamping forming groove 101. It can be used for a long time at 900 °C (the suitable forming temperature of titanium alloy), and has good insulation performance and heat preservation performance. The surface of the high-silica fiber cloth is smooth, which can improve the fluidity of the material and contribute to the improvement of the forming quality.

[0066] A groove-shaped annular thin plate electro-assisted forming process is also proposed, which is applied to the groove-shaped annular thin plate electro-assisted forming device as described above, and includes the following steps:

[0067] S1. Place the slab to be formed on the top surface of the lower die 1 and adjust the position of the slab. The slab is a rectangular plate with a fixed size and is placed at a preset position on the lower die 1, which can ensure that the outer shapes of the stamped parts formed by each slab are consistent, facilitating subsequent surplus material removal processing.

[0068] S2. The stamping lifting table 200 drives the upper die 2, the nitrogen spring 8, the stamping punch 3, the pre-pressing plate 5, the first electrode plate 6 and the second electrode plate 7 to move downward synchronously. The first electrode plate 6 and the second electrode plate 7 continue to move downward until they simultaneously contact both sides of the top surface of the slab, and through the self-weight of the pre-pressing plate 5 and the two electrode plates, pre-press both sides of the slab.

[0069] S3. The upper die 2 continues to move downward. The free ends of the nitrogen springs 8 contact both sides of the top surface of the slab and press the slab tightly on the top surface of the lower die 1, realizing the pressing of both sides of the slab, so that the area of the slab above the stamping forming groove 101 is the cavity area, and the areas on both sides of the stamping forming groove 101 are the flange areas. Since the formed part after stamping is S-shaped, the stresses generated by the stretching deformation of the rectangular slab at different positions in the length direction are different. Therefore, by setting the pressure values applied to the slab surface by the free ends of two adjacent nitrogen springs 8 to be different, and actively distributing different blank-holding forces to different curvature parts, the uniform forming of the thin-walled asymmetric special-shaped structure can be realized by using this non-uniformity.

[0070] S4. The first electrode plate 6 and the second electrode plate 7 are energized with opposite polarities, and a high-frequency pulsed current is passed into the slab for a preset time. In this step, through electro-assisted heating, the slab can be quickly heated to the appropriate forming temperature, improving the forming work efficiency and the uniformity of forming in each area.

[0071] S5. The electrode bar 4 is energized, the first electrode plate 6 and the second electrode plate 7 are energized with the same polarity, and have the opposite polarity to the electrode bar 4. In this equipment, each electrode bar 4 is respectively connected to the positive output port of the high-voltage pulse generator. Since the high-frequency pulsed current densities input by each electrode bar 4 are different, the electrode bars 4 with different input current densities are respectively connected to different output ports, and the same number of relays are set in the control circuit to realize the on-off control of the power supply circuit of each electrode bar 4. Similarly, relays are set for the power supply circuits of the first electrode plate 6 and the second electrode plate 7 to realize the automatic switching of the corresponding circuits.

[0072] S6. The stamping punch 3 continues to move downward. After contacting the top surface of the slab, the slab bends and deforms, and its surface contacts the electrode bars 4 from the inside out, and a high-frequency pulsed current is passed into the slab. After each electrode bar 4 is energized for the corresponding preset duration, it is powered off. The magnitude of the current density passed into each electrode bar 4 is inversely proportional to the thinning degree of the corresponding slab stretching area.

[0073] S7. After the stamping punch 3 descends to the lowest position, it holds pressure for a preset duration. The first electrode plate 6 and the second electrode plate 7 are energized with opposite polarities, and a low-frequency pulsed current is passed into the slab for a preset time. After stamping, the overall stress relaxation is achieved through electro-assisted heating, with a rapid decrease in residual stress and a reduction in springback, resulting in high surface accuracy of the formed part.

[0074] S8. The first electrode plate 6 and the second electrode plate 7 are de-energized, and the stamping lifting table 200 drives the upper die 2 to move upward and reset. After the stamped part cools, it is taken out from the lower die 2.

[0075] S9. The surplus materials on each side of the stamped part are removed to obtain a wavy linear grooved thin plate part, and then it is cut to form a grooved sector thin plate part. On the cutting line between two adjacent grooved sector thin plate parts, the end with a smaller radius of one grooved sector thin plate part is in the same position as the end with a larger radius of the adjacent grooved sector thin plate part. Therefore, the material structure stresses at the inner and outer ends are the same. As Figure 12 shown, the areas shown as Sa and Sb in the figure are two sector grooved thin plate parts obtained after cutting, and the areas shown as Sc and Sd are the surplus material areas that need to be removed at both ends. The flange plate areas adjacent to the wavy lines on both sides are not shown in the figure. As shown in the figure, in the top view direction of the sector grooved thin plate part, the connecting line of the centers corresponding to the arc edges is used as the cutting line, that is, the dotted line shown in the figure.

[0076] S10. The sector grooved thin plate parts are sequentially spliced and welded to form a grooved annular thin plate part. Since the material structure stresses at the inner and outer ends of each grooved sector thin plate part on the cutting line are the same, the stresses at each part are also the same after welding, presenting a state of uniform stress distribution as a whole.

[0077] Since the wavy linear grooved thin plate part formed by stamping is a continuous integral forming, that is, the large-curvature forming area of each grooved sector thin plate part is continuous with the small-curvature forming area of the adjacent grooved sector thin plate part, the forming performance of each part on the inner and outer sides of each grooved sector thin plate part after cutting can be ensured to be the same, thus significantly improving the overall quality of the grooved annular thin plate part formed after welding.

[0078] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0079] The above is only the embodiment of the present invention, and it does not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be included in the patent protection scope of the present invention by the same token.

Claims

1. An electrically assisted forming device for a grooved annular thin plate, comprising a lower die fixedly arranged on the top surface of a stamping workbench, and an upper die fixedly arranged on the bottom surface of a stamping lifting platform and located directly above the lower die, characterized in that: At least one row of nitrogen springs are fixedly arranged on both sides of the bottom of the upper die, a wave-shaped stamping groove is opened on the top surface of the lower die, a stamping punch matching the stamping groove is fixedly arranged on the bottom of the upper die, a plurality of electrode strips are fixedly arranged on the surface of the stamping punch along the length direction, a pre-pressing plate that can be raised and lowered is movably sleeved on the outer side of the stamping punch, and a first electrode plate and a second electrode plate are arranged on the bottom surface of the pre-pressing plate, which are respectively located on both sides of the stamping punch; Before the punch punch bends and deforms the slab, the two electrode plates are electrically opposite and contact both sides of the surface of the slab at the same time, and a high-frequency pulse current is passed through the slab for a preset time. During the bending and deformation of the slab, the two electrode plates are electrically the same and opposite to the electrode strips, and the surface of the slab is progressively contacted with the electrode strips from the center to both sides, and a high-frequency pulse current is passed through the slab for a corresponding preset time. After stamping is completed, the pressure is maintained, the two electrode plates have opposite electrical properties, and a low-frequency pulse current is passed into the slab for a preset time.

2. The electric-assisted forming device for a grooved annular thin plate according to claim 1, characterized in that: The bottom surface of the upper mold is respectively fixedly connected with spring mounting seats on both sides, and the bottom surface of the spring mounting seat is provided with a spring embedding groove. The nitrogen spring is fixedly embedded in the spring embedding groove, and the free end of the nitrogen spring movably penetrates below the bottom surface of the first electrode plate and the second electrode plate.

3. The electric-assisted forming device for a grooved annular thin plate according to claim 2, characterized in that: A punch mounting seat located between two spring mounting seats is fixedly connected to the middle of the bottom surface of the upper die, the stamping punch is fixedly connected to the bottom surface of the punch mounting seat, and a square through hole is opened in the pre-pressing plate and is located directly below the punch mounting seat.

4. The electric-assisted forming device for a grooved annular thin plate according to claim 2, characterized in that: Both sides of the top surface of the pre-pressing plate are respectively fixedly connected with lifting bolts, and the lifting bolts are movably arranged in the spring mounting seat.

5. The electric-assisted forming device for a grooved annular thin plate according to claim 1 or 4, characterized in that: Electrode plate embedding grooves are respectively opened on both sides of the bottom surface of the pre-pressing plate, and the first electrode plate and the second electrode plate are respectively embedded in the corresponding electrode plate embedding grooves. The bottom surfaces of the first electrode plate and the second electrode plate are located in the same horizontal plane and protrude from the bottom surface of the pre-pressing plate.

6. The electric-assisted forming device for a grooved annular thin plate according to claim 1, characterized in that: The surface of the punching groove is paved with high-silica fiber cloth.

7. A groove-shaped annular thin plate electrically assisted forming process, applied to the groove-shaped annular thin plate electrically assisted forming device as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Accurately place the slab to be formed on the top surface of the lower die; S2, the punching lifting platform drives the upper die and the components thereon to move downward synchronously, and the first electrode plate and the second electrode plate continue to move downward until they contact the top surface of the slab; S3, the free end of the nitrogen spring contacts both sides of the top surface of the slab and presses the slab tightly; S4, two electrode plates are energized with opposite electrical properties, and a high-frequency pulse current is passed into the slab for a preset time; S5. The electrode strip is energized, and the two electrode plates are energized with the same electrical properties, which are opposite to the electrical properties of the electrode strip; S6, the punching punch continues to move downward, and after contacting the top surface of the slab, the slab is bent and deformed so that its surface contacts the electrode strips from the inside to the outside, respectively, and a high-frequency pulse current is passed into the slab, and each electrode strip is energized for a corresponding preset time and then disconnected; S7, after the punch moves downward to the lowest position, the pressure is maintained for a preset time, the two electrode plates are energized with opposite electrical properties, and a low-frequency pulse current is passed into the slab for a preset time; S8, the two electrode plates are powered off, the upper die moves upward and resets, and the stamping parts are taken out after cooling; S9, removing excess material to obtain a wave-shaped slotted thin plate, and cutting to form slotted fan-shaped thin plate; S10, the fan-shaped grooved thin plate parts are spliced ​​and welded in sequence to form a grooved annular thin plate part.

8. The process for electrically assisting the forming of a grooved annular thin plate according to claim 7, characterized in that: In step S3, the pressure values ​​applied by the free ends of two adjacent nitrogen springs to the surface of the slab are different.

9. The process for electrically assisting the forming of a grooved annular thin plate according to claim 7, characterized in that: In step S6, the current density flowing through each electrode strip is inversely proportional to the thinning degree of the corresponding slab stretching area.

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