Electric auxiliary forming device and technology for groove-shaped annular plate

Abstract

The invention discloses an electric auxiliary forming device and process for a groove-shaped annular plate. The electric auxiliary forming device comprises a lower die and an upper die fixedly arranged over the lower die, the two sides of the bottom of the upper die are each fixedly provided with at least one row of nitrogen springs, and the top face of the lower die is provided with a wavy-line-shaped stamping forming groove; a stamping male die matched with the stamping forming groove is fixedly arranged at the bottom of the upper die, a plurality of electrode strips are fixedly arranged on the surface of the stamping male die in the length direction, the outer side of the stamping male die is movably sleeved with a liftable pre-pressing plate, and a first electrode plate and a second electrode plate which are located on the two sides of the stamping male die respectively are arranged on the bottom face of the pre-pressing plate. According to the device, a wave line type groove-shaped thin plate can be punched at a time, and then a plurality of groove-shaped fan-shaped thin plates with the same specification are formed through cutting, so that a groove-shaped annular plate can be formed through splicing; stamping forming of a final part is comprehensively achieved in a partitioned power-up mode, and the forming work efficiency and the uniformity of all areas are improved.

Description

Technical Field

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

[0002] Aircraft include spacecraft, carriers and upper stages. The upper stage is the last stage or multi-stage rocket in a multi-stage launch vehicle that is independent of the basic stage. The upper stage of the launch vehicle is a key structure in aerospace technology, and it has put forward an extremely urgent demand for the development and production of large-sized or ultra-large-sized annular tanks with large capacity. There are three key technical challenges in the high-precision forming of annular tanks: First, the shape is very complex, including large size and small features, as well as complex features such as significantly different curvatures, special-shaped closed sections, ultra-large feature sizes and ultra-thin wall thicknesses. These features make the deformation of the blank far exceed the limit value of the formation of defects in traditional processes; second, the material is a difficult-to-deform alloy, and titanium alloys have poor room temperature forming properties and high yield strength; third, dimensional accuracy and strength and plasticity matching are required. Due to its ultra-thin characteristics, the annular tank cannot be formed and then processed, so the forming accuracy must be guaranteed by direct forming. The challenges of the above key technologies are coupled and superimposed on each other, making the manufacturing of components extremely difficult. Existing forming technologies based on rigid molds cannot form such complex integral structures due to the limitation of loading space. Therefore, such components are often decomposed into simple small-sized components (usually uniform fan shapes) and then welded into integral annular components after forming.

[0003] The traditional hot forming process has the following shortcomings: the traditional hot forming equipment is mainly heating furnace and press, large-size annular storage box is difficult to transport, and there are warping and heat dissipation phenomena during transportation. The heat dissipation temperature drop within 1 minute is as high as 300℃, so the heat energy consumption of the sheet is large. The high-temperature ultra-thin sheet of 800℃ is in contact with the cold mold of 20℃, and the heat is transferred from the high-temperature object to the low-temperature object. The temperature drop of the high-temperature ultra-thin sheet is fast, the material fluidity decreases, and the forming quality is poor; in order to solve the problem of forming temperature drop, it is necessary to increase the preheating temperature of the ultra-thin sheet, but the higher the temperature, the stronger the oxidation degree of the titanium alloy. 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. After heating to the preset temperature, it still needs to be kept warm for a period of time. The internal structure and properties of the material change, which is quite different from the original structure. The component is formed at the cost of changing the structure and properties; there is an obvious rebound phenomenon in the stamping process of the ultra-thin sheet, and subsequent heat treatment experiments are required to achieve the purpose of stress relaxation.

[0004] At the same time, during the individual forming process of large-sized components, due to the inconsistent curvature of the inner and outer sides, it is easy to have problems such as uneven stress and premature breakage, resulting in a high scrap rate. Summary of the invention

[0005] In view of the above-mentioned defects and shortcomings, the present invention provides an electrically assisted forming device and process for a grooved annular plate. By setting a wavy-line stamping forming groove and a matching stamping punch, a wavy-line grooved thin plate part can be punched out at one time, and then cut to form multiple grooved fan-shaped thin plate parts of the same specifications, which can be spliced ​​to form a grooved annular plate part; by designing a flange area and a cavity area for the slab, a clamping force is provided to the flange area and a part forming stamping force is provided to the cavity area, and a zoned power-on method is adopted to comprehensively realize the stamping forming of the final part, thereby improving the forming work efficiency and the uniformity of each area.

[0006] In order to solve the above technical problems, a technical solution adopted by the present invention is: A groove-shaped annular thin plate electric-assisted forming device comprises a lower die fixedly arranged on the top surface of a stamping workbench, an upper die fixedly arranged on the bottom surface of a stamping lifting platform and located directly above the lower die, at least one row of nitrogen springs are fixedly arranged on both sides of the bottom of the upper die, a wave-shaped stamping forming groove is opened 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 strips are fixedly arranged on the surface of the stamping punch along the length direction, a pre-pressing plate that can be lifted and lowered is movably sleeved on the outer side of the stamping punch, and a first electrode plate and a second electrode plate respectively located on both sides of the stamping punch are arranged on the bottom surface of the pre-pressing plate; Before the stamping punch stamps the slab into a bending shape, the first electrode plate and the second electrode plate are in contact with both sides of the surface of the slab at the same time, the two electrode plates have opposite electrical properties, and a high-frequency pulse current is passed through the slab for a preset time; during the stamping punch stamping the slab into a bending shape, the two electrode plates have the same electrical properties and are opposite to the electrical properties of the electrode strips, the surface of the slab is in contact with the electrode strips in sequence from the center to both sides, and a high-frequency pulse current is passed through the slab for a corresponding preset time; when the stamping punch is pressed and the pressure is maintained after the stamping is completed, the two electrode plates have opposite electrical properties, and a low-frequency pulse current is passed through the slab for a preset time.

[0007] Furthermore, the stiffness coefficients of two adjacent nitrogen springs are different and the free end lengths are the same, or the stiffness coefficients of two adjacent nitrogen springs are the same and the free end lengths are different.

[0008] Furthermore, spring mounting seats are fixedly connected to both sides of the bottom surface of the upper mold, and a spring embedding groove is opened on the bottom surface of the spring mounting seat. The nitrogen spring is fixedly embedded in the spring embedding groove, and the free end of the nitrogen spring moves through the bottom surface of the first electrode plate and the second electrode plate.

[0009] Furthermore, 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 directly below the punch mounting seat.

[0010] Furthermore, 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.

[0011] Furthermore, electrode plate 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 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.

[0012] Furthermore, a plurality of terminal embedding grooves are provided in the outer side surfaces of the first electrode plate and the second electrode plate, and connection terminals are arranged in the terminal embedding grooves.

[0013] Furthermore, the surface of the stamping groove is paved with high-silica fiber cloth.

[0014] A groove-shaped annular thin plate electrically assisted forming process is also provided, which is applied to the groove-shaped annular thin plate electrically assisted forming device as described above, and comprises the following steps: S1. Place the slab to be formed on the top surface of the lower die and adjust the position of the slab; S2, the stamping lifting platform drives the upper die, nitrogen spring, stamping punch, pre-pressing plate, first electrode plate and second electrode plate to move downward synchronously, and the first electrode plate and second electrode plate continue to move downward until they are in contact with the top surface of the slab at the same time; S3, the free end of the nitrogen spring contacts both sides of the top surface of the slab and presses the slab tightly against the top surface of the lower die; S4, the first electrode plate and the second electrode plate are energized with opposite electrical properties, and a high-frequency pulse current is passed into the slab for a preset time; S5, the electrode strips are energized, the first electrode plate and the second electrode plate are energized and have the same electrical properties, which are opposite to those of the electrode strips; 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 first electrode plate and the second electrode plate are energized with opposite electrical properties, and a low-frequency pulse current is passed into the slab for a preset time; S8, the first electrode plate and the second electrode plate are powered off, the stamping lifting platform drives the upper die to reset upward, and the stamping part is taken out from the lower die after cooling; S9, removing the excess material on each side of the stamping part to obtain a wave-shaped groove-shaped thin plate part, and then cutting to form a groove-shaped fan-shaped thin plate part; S10, splicing and welding the fan-shaped grooved thin plate parts in sequence to form a grooved annular thin plate part.

[0015] Furthermore, in step S3, the pressure values ​​applied by the free ends of two adjacent nitrogen springs to the surface of the slab are different.

[0016] Furthermore, in step S6, the current density flowing through each electrode strip is inversely proportional to the thinning degree of the corresponding slab stretching region.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention provides a wave-shaped stamping groove and a matching stamping punch, so that a wave-shaped groove-shaped thin plate can be stamped out at one time, and then cut to form a plurality of groove-shaped fan-shaped thin plate parts of the same specification, so that the groove-shaped annular thin plate parts can be spliced ​​to realize the miniaturization production of components of large workpieces; 2. Since the wave-shaped slot-shaped thin plate formed by stamping is formed continuously as a whole, that is, the large curvature forming area of ​​each slot-shaped fan-shaped thin plate is continuous with the small curvature forming area of ​​the adjacent slot-shaped fan-shaped thin plate, it can ensure that the forming performance of the inner and outer sides of each slot-shaped fan-shaped thin plate after cutting is the same, thereby significantly improving the overall quality of the slot-shaped annular thin plate formed after welding; 3. The forming device of the present invention designs flange area and cavity area for the slab, provides blanking force for the flange area and part forming punching force for the cavity area, and adopts the method of zoned power-on to comprehensively realize the stamping forming of the final part, thereby improving the forming work efficiency and the uniformity of forming in each area. By passing high-frequency pulse currents with different current densities into different forming areas of the slab to realize electric auxiliary heating, the material in the local area can be prevented from being excessively thinned after the mold is closed, resulting in excessive local temperature, so as to achieve a more uniform overall material temperature and effectively reduce the risk of thin areas being broken down by high pulse currents; 4. The present invention realizes rapid heating of the plate blank by adopting electric auxiliary heating, which can effectively improve the heating efficiency of the plate blank, avoid the plate blank being in a heated state for a long time, avoid grain coarsening and performance degradation of the internal structure of the material, thereby improving the surface forming quality of the semi-formed part. After stamping, the whole part is electrically heated to achieve stress relaxation, the residual stress decreases quickly, and the springback is reduced, so that the surface accuracy of the formed part is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is one of the three-dimensional structural schematic diagrams of the electric-assisted forming device of the present invention; Figure 2 The second schematic diagram of the three-dimensional structure of the electric-assisted forming device of the present invention; Figure 3 It is one of the three-dimensional structural schematic diagrams of the upper mold and the components thereon; Figure 4 The second is a schematic diagram of the three-dimensional structure of the upper mold and the components thereon; Figure 5 One of the three-dimensional structural schematic diagrams of two electrode plates assembled on a pre-pressing plate; Figure 6 The second is a three-dimensional structural schematic diagram of two electrode plates assembled on a pre-pressing plate; Figure 7 It is a three-dimensional structural schematic diagram of the distribution state of the wiring terminals in the electrode plate; Figure 8 is a schematic diagram of the three-dimensional structure of the stamping punch and the electrode strip; Fig. 9 is a schematic diagram of the three-dimensional structure of the lower mold; Fig.10 It is a schematic diagram of the slab being pressed on the lower die; Fig.11 A schematic diagram of the three-dimensional structure of a wave-shaped groove-shaped thin plate prepared by the present invention; Fig.12 A schematic diagram of the cutting position for cutting a wave-shaped grooved thin plate piece into a grooved fan-shaped thin plate piece; Fig.13 A schematic diagram of the three-dimensional structure of a grooved fan-shaped thin plate member prepared by the present invention; Fig.14 This is a schematic diagram of the three-dimensional structure of the grooved annular thin plate member prepared in the present invention.

[0019] In the figure: 1. lower die; 101. stamping forming groove; 2. upper die; 3. stamping punch; 4. electrode strip; 5. pre-pressing plate; 501. limiting countersunk hole; 502. positioning column; 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. terminal; 100. stamping workbench; 200. stamping lifting platform. DETAILED DESCRIPTION

[0020] The preferred embodiments of the present invention are described in detail below 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.

[0021] It should be noted that when a component is referred to as being "mounted on" another component, it may be directly on the other component or there may be a central component. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be a central component at the same time. When a component is considered to be "fixed to" another component, it may be directly fixed on the other component or there may be a central component at the same time.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention 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.

[0023] The present invention provides an electric-assisted forming device for grooved annular thin plate parts, which is used to prepare Fig.11 The wavy groove-shaped thin plate member shown in the figure is then formed by the wavy groove-shaped thin plate member along the Fig.12 The cutting position shown by the dotted line in the figure is cut to form Fig.13 The grooved fan-shaped thin plate parts shown in the figure are then spliced ​​and welded to form the grooved fan-shaped thin plate parts as shown in the figure. Fig.14 The grooved annular thin plate shown. When the electric-assisted forming device is actually used, it cooperates with the existing stamping forming equipment, high-voltage pulse generator and circuit switching control system to realize power supply and control, current supply and circuit switching logic control, which are all existing technologies and will not be described here.

[0024] See also Figures 1 to 10 The electric-assisted forming device comprises a lower die 1 fixedly arranged on the top surface of a stamping workbench 100, and an upper die 2 fixedly arranged on the bottom surface of a stamping lifting platform 200 and located directly above the lower die 1. The stamping lifting platform 200 drives the upper die 2 and its components to move up and down to complete the closing and opening process of the upper and lower dies. Fig. 9 As shown, a wavy stamping groove 101 is provided on the top surface of the lower die 1. The stamping groove 101 is a curved groove with a semicircular cross-section and a wavy path. The wavy path is an arc line with a continuous curvature and the same radius, that is, the offset distances of the two side edges of the top of the stamping groove and the wavy path are equal. In the drawings of this embodiment, a single wavy slot-shaped thin plate piece can be cut to form two slot-shaped fan-shaped thin plate pieces for illustration.

[0025] The bottom of the upper die 2 is fixedly provided with a punch 3 matching the punching groove 101. Specifically, the middle part of the bottom surface of the upper die 2 is fixedly connected with a punch mounting seat 10 by bolts, and the punch 3 is fixedly connected to the bottom surface of the punch mounting seat 10 by bolts, so that the punch 3 and the upper die 2 are rigidly connected, thereby providing power for the downward movement of the punch 3 and the bending deformation of the slab. By setting a wavy-line punching groove and a matching punch 3, a wavy-line groove-shaped thin plate can be punched out at one time, and then a plurality of groove-shaped fan-shaped thin plate parts of the same specifications can be cut to form a groove-shaped annular thin plate part, which can be spliced ​​to form a groove-shaped annular thin plate part, realizing the miniaturized production and manufacturing of components of large workpieces.

[0026] The outer side of the punching punch 3 is movably sleeved with a pre-pressing plate 5 that can be raised and lowered, and the bottom surface of the pre-pressing plate 5 is provided with a first electrode plate 6 and a second electrode plate 7 located on both sides of the punching punch 3. Specifically, the top surface of the pre-pressing plate 5 is respectively threadedly connected with lifting bolts 11, and the bare rod part of the lifting bolt 11 is movably penetrated and arranged in the spring mounting seat 9. The lifting bolt 11 adopts a plug screw, and its screw rod part is sleeved with a sleeve. A threaded connection hole 504 is provided on the top surface of the pre-pressing plate 5, and the threaded end of the lifting bolt 11 is threadedly connected in the threaded connection hole 504; a vertically arranged countersunk hole is provided inside the spring mounting seat 9, and the sleeve is located in the small diameter hole of the countersunk hole; a through hole with the same diameter as the large diameter hole of the countersunk hole is provided in the top surface of the upper mold 2, and the nut part of the lifting bolt 11 is movably raised and lowered in the through hole and the large diameter hole of the countersunk hole. In the free state without mold clamping, the pre-pressing plate 5 is located at the lowest vertical position and is located below the lowest end of the punching 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 contact both sides of the top surface of the slab at the same time. During the process of the upper die 2 driving the stamping punch 3 to continue to descend, the lifting bolt 11 moves upward relative to the spring mounting seat 9, and the pre-compression plate 5 applies pressure to the first electrode plate 6 and the second electrode plate 7 by its gravity, so that the first electrode plate 6 and the second electrode plate 7 are in reliable contact with the top surface of the slab, thereby pre-compressing the forming position on both sides of the top surface of the slab.

[0027] At least one row of nitrogen springs 8 are fixedly arranged on both sides of the bottom of the upper die 2. 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 by bolts, and a spring embedding groove is provided on the bottom surface of the spring mounting seat 9. The nitrogen springs 8 are fixedly embedded in the spring embedding groove, so that each nitrogen spring 8 is pre-fixed on the spring mounting seat 9 according to a preset arrangement order, and then fixedly assembled on the upper die 2 as a whole.

[0028] After the first electrode plate 6 and the second electrode plate 7 pre-compact the slab, the bottom output end of the nitrogen spring 8 penetrates the pre-compacting plate 5 and contacts the top surface of the slab during the process of the upper mold 2 continuing to move downward, and then applies a pressing force to the top surface of the slab through the force generated by its own compression, thereby pressing the slab tightly against the lower mold 1. In the process of compacting the slab, the nitrogen spring 8 also plays a buffering role in the mold closing process between the upper mold 2 and the lower mold 1. Since the slab is rectangular and the cavity area of ​​the stamping forming is wavy, the blanking force required for different curvature parts is different during the actual stamping and stretching process. Therefore, by actively allocating different blanking forces to different curvature parts, this unevenness can be used to achieve 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 former type of nitrogen spring 8 is selected. In this way, in the process of the upper mold 2 driving the nitrogen springs 8 to move downward synchronously, for the nitrogen springs with the former distribution type, the free ends of the nitrogen springs 8 are in contact with the surface of the slab at the same time, so that the free ends of the nitrogen springs 8 are compressed by the same distance. Due to the different stiffness coefficients, the local clamping forces acting on the surface of the slab are also different; for the nitrogen springs with the latter distribution form, the nitrogen springs with longer free ends contact the surface of the slab first, and the nitrogen springs with shorter free ends contact the surface of the slab later, so that the free ends of the nitrogen springs 8 are compressed to different lengths. Due to the same stiffness coefficients, the local clamping forces acting on the surface of the slab are also different.

[0029] Electrode plate embedding grooves are respectively provided on both sides of the bottom surface of the pre-pressing plate 5, and the first electrode plate 6 and the second electrode plate 7 are respectively embedded in the corresponding electrode plate embedding grooves and fixedly connected by bolts. Furthermore, positioning columns 502 are fixedly provided in the electrode plate embedding grooves, and positioning holes are provided in 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, thereby ensuring that the first electrode plate 6 and the second electrode plate 7 are both reliably in contact with the top surface of the slab.

[0030] A square through hole 503 is provided in the pre-pressing plate 5, which is located directly below the punch mounting seat 10, so that when the upper die 2 drives the punching punch 3 to continue to move downward, the punching punch 3 and the punch mounting seat 10 can pass through the square through hole to complete the subsequent stamping process. A limiting countersunk hole 501 is provided on the top surface of the pre-pressing plate 5, which is located directly below the nitrogen spring 8 and on one side of the square through hole 503. The major diameter of the limiting countersunk 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 in the countersunk hole 501, and the minor diameter of the limiting countersunk 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, so as to ensure that the free end of the nitrogen spring 8 can smoothly pass through the pre-pressing plate 5. After the bottom surfaces of the first electrode plate 6 and the second electrode plate 7 contact the top surface of the slab, as the nitrogen spring 8 and the spring mounting seat 9 move 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-compression plate 5. When the stamping punch 3 descends to the lowest position, the bottom end of the main body of the nitrogen spring 8 is located above the top surface of the pre-compression plate 5, or extends into the limiting countersunk hole 501 and is located above the bottom surface of the groove of the limiting countersunk hole 501, thereby ensuring that the bottom end of the main body of the nitrogen spring 8 will not produce rigid contact with the pre-compression plate 5, so that the pre-compression plate 5, the first electrode plate 6 and the second electrode plate 7 will not produce motion interference with the edge pressing action between the nitrogen spring 8 and the slab.

[0031] After the first electrode plate 6 and the second electrode plate 7 are in contact with the top surface of the slab and before the bottom end of the punch 3 is in contact with the top surface of the slab, 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 first electrode plate 6 and the second electrode plate 7 have opposite electrical properties, so that a high-frequency pulse current is passed through the slab for a preset time (the specific time is determined according to the appropriate stamping forming temperature of the slab and the current density of the high-frequency pulse current), which can achieve rapid heating of the slab as a whole and make the slab at an appropriate deformation temperature. The rapid heating of the slab by power-assisted heating can effectively improve the heating efficiency of the slab, avoid the slab being in a heated state for a long time, and avoid grain coarsening and performance degradation of the internal structure of the material, so that the surface forming quality of the semi-formed part is better.

[0032] In order to improve the uniformity of the current density distribution in the first electrode plate 6 and the second electrode plate 7, a plurality of (in this embodiment, as shown in FIG. Figure 7 The terminal embedding groove 601 is provided with a connection terminal 12 and fixed in the terminal embedding groove 601 by bolts. Pulse currents with the same parameters are synchronously introduced through multiple connection terminals 12 to avoid large differences in current density on the top surface of the slab caused by the resistance of the first electrode plate 6 and the second electrode plate 7.

[0033] A plurality of electrode strips 4 are fixedly arranged on the surface of the punch 3 along the length direction. Figure 4 and Figure 8 As shown, in this embodiment, the number of electrode strips 4 is 5, and they are evenly distributed along the semicircular arc profile of the cross section of the punch 3. The surface of the punch 3 is provided with electrode strip embedding grooves along its length direction, and the electrode strips 4 are respectively fixedly embedded in the electrode strip embedding grooves to prevent the electrode strips 4 from changing their positions during the punching process, and the surface of the electrode strips 4 protrudes parallel to the surface of the punch 3, and the protruding height is preferably to ensure that the electrode strips 4 can reliably contact the surface of the slab and do not affect the bending process of the slab.

[0034] After the first electrode plate 6 and the second electrode plate 7 heat 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 strip 4 is 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 electrical properties and are opposite to the electrical properties of the electrode strip 4. The punch 3 continues to move downward and begins to contact the center of the top surface of the slab, applying a stamping forming force to the slab, causing the slab to begin to bend and deform. At the same time, the electrode strip 4 (located at the bottom of the punch 3) on the surface of the punch 3 Figure 8 The electrode strip 4 is in contact with the top surface of the slab at the middle position shown in the figure, and the electrode strip 4 cooperates with the first electrode plate 6 and the second electrode plate 7 respectively, and a high-frequency pulse current is passed through the two side areas of the slab for a corresponding preset time to quickly heat the forming area of ​​the slab, compensate for the heat loss, and maintain the forming area within a suitable deformation temperature range.

[0035] As the slab continues to bend and deform, the forming areas on both sides gradually bend upward and contact the two side surfaces of the bottom of the stamping punch 3, so that the two electrode strips 4 on both sides above the lowest electrode strip 4 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 lowest electrode strip 4 is in a power-off state), and then respectively cooperate with the first electrode plate 6 and the second electrode plate 7 to pass high-frequency pulse current through the two side areas of the slab for the corresponding preset time, so as to quickly heat the forming area of ​​the slab, compensate for heat loss, and maintain the forming area within a suitable deformation temperature range. During this process, since the middle part of the slab has been stretched and deformed first and bent, the local material thickness is thinned. If the power is continued to be turned on for heating, excessive thinning may occur, resulting in local excessive temperature or even breakdown and fracture. Therefore, the bottom electrode strip 4 is in a power-off state; and since the heat loss rate from the center of the slab to the sides gradually increases, the outer electrode strips 4 are sequentially replaced by power, so that the heating energy of the two outer bending forming areas of the plate can be supplemented, and the heat supply to the formed part between the two forming areas can be stopped, so that the forming performance of the formed part is reduced to avoid further thinning due to subsequent stretching deformation; further, since the amount of deep drawing and thinning in different deformation areas is different, the high-frequency current density in different deformation areas should be different. The current density of each electrode strip 4 is inversely proportional to the thinning degree of the corresponding slab stretching area (the stamping speed can be considered constant, that is, the preset heating time of each electrode strip 4 can be considered the same), so as to avoid excessive thinning of the material in the local area after the mold is closed, resulting in local excessive temperature. The two electrode strips 4 located on the uppermost sides of the surface of the punch 3 use the same method to quickly heat the forming area during the bending and deformation of the slab (the three electrode strips 4 located on the inner side are all in a power-off state at this time). By passing high-frequency pulse currents with different current densities through different forming areas of the slab to achieve electric auxiliary heating, it is possible to avoid the phenomenon of excessive thinning of the material in a local area after the mold is closed, resulting in excessive local temperature, so as to achieve a more uniform temperature of the entire material and effectively reduce the risk of breakdown of the thin area by high pulse current.

[0036] Preferably, the surface of the stamping groove 101 is paved with high-silica fiber cloth. It can be used for a long time at 900°C (the suitable forming temperature of titanium alloy) and has good insulation and heat preservation properties. The high-silica fiber cloth has a smooth surface, which can improve the fluidity of the material and help improve the forming quality.

[0037] A groove-shaped annular thin plate electrically assisted forming process is also proposed, which is applied to the groove-shaped annular thin plate electrically assisted forming device as described above, and comprises the following steps: 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 of fixed size and is placed at a preset position on the lower die 1 to ensure that the stamping parts formed after stamping each slab are consistent in shape, which is convenient for subsequent excess material removal processing.

[0038] S2, the stamping lifting platform 200 drives the upper mold 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, and the first electrode plate 6 and the second electrode plate 7 continue to move downward until they contact both sides of the top surface of the slab at the same time, and the pre-pressing plate 5 and the weight of the two electrode plates are used to pre-tighten both sides of the slab.

[0039] S3, the upper die 2 continues to move downward, the free ends of the nitrogen spring 8 contact both sides of the top surface of the slab and press the slab tightly against the top surface of the lower die 1, so that the slab is pressed tightly on both sides, so that the area above the stamping groove 101 of the slab is the cavity area, and the area on both sides of the stamping groove 101 is the flange area. Since the formed part after stamping is S-shaped, the stress generated by the tensile deformation of the rectangular slab at different positions in the length direction is different. Therefore, by setting different pressure values ​​applied to the slab surface by the free ends of two adjacent nitrogen springs 8, different blanking forces are actively allocated to different curvature parts, and this unevenness can be used to achieve uniform forming of thin-walled asymmetric special-shaped structures.

[0040] S4, the first electrode plate 6 and the second electrode plate 7 are powered on and have opposite electrical properties, and a high-frequency pulse current is passed into the slab for a preset time. In this step, the slab can be quickly heated to a suitable forming temperature through electrical auxiliary heating, thereby improving the forming work efficiency and the uniformity of forming in each area.

[0041] S5, the electrode strip 4 is powered on, the first electrode plate 6 and the second electrode plate 7 are powered on and have the same electrical properties, which are opposite to the electrical properties of the electrode strip 4. In this device, each electrode strip 4 is respectively connected to the positive output port of the high-voltage pulse generator. Since the high-frequency pulse current density input to each electrode strip 4 is different, the electrode strips 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 strip 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.

[0042] S6, the punch 3 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 4 from the inside to the outside, respectively, and a high-frequency pulse current is passed into the slab, and each electrode strip 4 is powered on for a corresponding preset time and then powered off. The current density of each electrode strip 4 is inversely proportional to the thinning degree of the corresponding slab stretching area.

[0043] S7, after the punch 3 descends to the lowest position, the pressure is maintained for a preset time, the first electrode plate 6 and the second electrode plate 7 are energized with opposite electrical properties, and a low-frequency pulse current is passed into the slab for a preset time. After stamping, the whole is electrically assisted to achieve stress relaxation, the residual stress decreases quickly, the springback is reduced, and the surface accuracy of the formed part is high.

[0044] S8, the first electrode plate 6 and the second electrode plate 7 are powered off, the stamping lifting platform 200 drives the upper die 2 to move upward and reset, and the stamped part is taken out from the lower die 2 after cooling.

[0045] S9, remove the excess material on each side of the stamping part to obtain a wavy line grooved thin plate part, and then cut it to form a grooved fan-shaped thin plate part. On the cutting line of two adjacent grooved fan-shaped thin plate parts, the end with a smaller radius of one grooved fan-shaped thin plate part and the end with a larger radius of the adjacent grooved fan-shaped thin plate part are at the same position, so the material organization stress at the inner and outer ends is the same. Fig.12 As shown in the figure, the areas Sa and Sb shown in the figure are the two fan-shaped slotted thin plate parts obtained after cutting, the areas Sc and Sd shown in the figure are the residual areas that need to be removed at both ends, and 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 direction of looking down at the fan-shaped slotted thin plate part, the line connecting the centers of the arc edges corresponding to the circle is used as the cutting line, that is, the dotted line shown in the figure.

[0046] S10, splicing and welding the fan-shaped slotted thin plate pieces in sequence to form a slotted annular thin plate piece. Since the material tissue stress at the inner and outer ends of each slotted fan-shaped thin plate piece on the cutting line is the same, the stress at each location after welding is also the same, and the overall stress is uniformly distributed.

[0047] Since the wavy grooved thin plate parts formed by stamping are formed continuously as a whole, that is, the large curvature forming area of ​​each grooved fan-shaped thin plate part is continuous with the small curvature forming area of ​​the adjacent grooved fan-shaped thin plate part, it can be ensured that the forming performance of the inner and outer sides of each grooved fan-shaped thin plate part after cutting is the same, thereby significantly improving the overall quality of the grooved annular thin plate parts formed after welding.

[0048] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, 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, they should be considered to be within the scope of this specification.

[0049] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. An electric-assisted forming device for a grooved annular thin plate, comprising a lower die and an upper die fixedly arranged thereon, 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. An electrically assisted forming process for a grooved annular thin plate, 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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