Extrusion forming device for magnesium alloy thin-wall inner-ring high-rib component

Abstract

The extrusion forming device of the magnesium alloy thin-wall inner-ring high-rib component comprises a female die, a male die and a pulse current device, a magnesium alloy blank is cylindrical, and a blank inner cavity is formed in the center of the magnesium alloy blank; a cavity with an opening in the top side is formed in the female die, and a magnesium alloy blank is embedded into the cavity downwards; the male die is located over the cavity and ascends and descends, a plurality of ribs are transversely arranged on the side wall of the male die in a protruding mode, the ribs are longitudinally arranged at intervals, grooves are formed between the adjacent ribs, the male die is composed of a plurality of petal parts, the petal parts can be transversely away from each other and expand outwards, and after the male die is inserted into the inner cavity of the blank, the inner wall of the inner cavity of the blank is extruded through the ribs. Filling the groove with a magnesium alloy blank; and a cathode and an anode of the pulse current device are electrically connected with the male die and the female die respectively, so that the ribs can perform partial discharge on the magnesium alloy blank. The fluidity of the magnesium alloy blank is effectively improved, the extrusion resistance is reduced, the magnesium alloy blank is filled in the groove, the forming precision is improved, and the integrated thin-wall high-rib component is formed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal plastic forming, in particular to an extrusion forming device for a magnesium alloy thin-wall inner ring high-fillet component. BACKGROUND

[0002] The integrated thin-wall high-fillet component is a key carrier for breaking through the technical bottleneck of large carrying capacity, low energy consumption and high reliability in aerospace and strategic equipment (such as large carrying capacity rockets, missile shells and underwater vehicles), and the performance of the component directly determines the core competitiveness of the equipment.

[0003] Currently, using a light and high-strength magnesium alloy component is an ideal choice to achieve extreme lightweight, however, the difficult deformation characteristics of magnesium alloy and the complex geometric characteristics of the extreme coupling of thin-wall and high-fillet size make the traditional manufacturing technology face many problems such as insufficient forming precision, high defect rate and substandard performance. When the traditional rotary extrusion technology is used to extrude the magnesium alloy blank, local strain mismatch is easily caused, which in turn induces defects such as folding and incomplete filling, resulting in low forming precision of the magnesium alloy thin-wall inner ring high-fillet component. SUMMARY

[0004] The purpose of the present application is to provide an extrusion forming device for a magnesium alloy thin-wall inner ring high-fillet component, which solves the technical problem of high forming precision of the integrated magnesium alloy thin-wall high-fillet component.

[0005] To achieve the above purpose, the solution of the present application is as follows: an extrusion forming device for a magnesium alloy thin-wall inner ring high-fillet component, comprising a female die, a male die and a pulse current device, the magnesium alloy blank is in a cylindrical shape, and the center is a blank inner cavity; The female die forms a cavity with a top side opening, and the cavity is for the magnesium alloy blank to be embedded downward; The male die is located directly above the cavity and can be raised and lowered, and after the magnesium alloy blank is embedded in the cavity, the male die can be lowered to insert into the blank inner cavity and raised to exit the blank inner cavity; The lateral wall of the male die is transversely protruded with a plurality of fillets, and the plurality of fillets are longitudinally spaced apart to form grooves between adjacent fillets, and the male die is composed of a plurality of petal parts, each petal part can be transversely expanded outward to fill the grooves with the magnesium alloy blank after the male die is inserted into the blank inner cavity by extruding the inner wall of the blank inner cavity with the fillets; The cathode and anode of the pulse current device are respectively electrically connected to the male die and the female die, so that the male die, the magnesium alloy blank, the female die and the pulse current device are sequentially conducted to form a current loop, so that the fillets can locally discharge the magnesium alloy blank when the fillets abut against the magnesium alloy blank.

[0006] Further, the end faces of the two adjacent fillets form flow guide surfaces on both sides of the groove entrance, and the two flow guide surfaces are respectively inclined towards the direction of the groove.

[0007] Further, the included angle between the two flow guide surfaces on both sides of the groove entrance is 135-145 degrees.

[0008] Further, the cross-sectional profile of the bottom wall of the groove is arc-shaped, and the middle part of the bottom wall bulges towards the end part of the rib to form a back pressure area, and the two sides of the bottom wall extend away from the end part of the rib.

[0009] Further, the cross section of the groove is a crescent structure.

[0010] Further, the inner contour of the blank cavity is circular with a radius R1, and the outer contour of the end part of the rib is arc-shaped with a radius R2, and R1 is greater than R2, so that the point contact between the end part of the rib and the blank cavity gradually changes into line contact when the convex mold laterally extrudes the blank cavity.

[0011] Further, the end part of the rib is embedded with an electrode contact, the electrode contact is strip-shaped and extends circumferentially along the end part of the rib, and the electrode contact protrudes from the end part of the rib, and the pulse current device is connected to the electrode contact through a wire, and the electrode contact locally discharges the magnesium alloy blank before the convex mold extrudes the blank cavity.

[0012] Further, the concave mold can be horizontally rotated to enable the convex mold to extrude different positions of the inner wall of the blank cavity to form an annular rib.

[0013] Further, the upper mold plate and the driving member are further included, the plurality of petals are radially slidably arranged at the bottom side of the upper mold plate through a sliding assembly, the driving member is arranged between the plurality of petals and is raised and lowered relative to the plurality of petals, the driving member is cylindrical, the bottom thereof is downwardly inclined and inwardly recessed to be conical to form a first inclined surface, and the plurality of petals form a second inclined surface on the side thereof facing the driving member to fit the first inclined surface, so that the plurality of petals are simultaneously radially expanded outwardly when the driving member is lowered, and the sliding assembly drives the plurality of petals to be radially close to each other when the driving member is raised. Insulating members are arranged between the plurality of petals and the upper mold plate, and insulating members are arranged between the plurality of petals and the driving member.

[0014] Further, the convex mold is made of copper-tungsten alloy, and the concave mold is made of steel.

[0015] After the above scheme is adopted, the beneficial effects of the present application are as follows: (1) Firstly, the male die can be lifted up and down, after descending into the cavity of the blank, it can be opposite to the inner wall of the cavity of the blank, and the plurality of petal parts can be expanded outward transversely, extruding the inner wall of the cavity of the blank, at the same time, the pulse current device is electrically connected to the male die and the female die respectively, when the rib abuts against the magnesium alloy blank, the rib can locally discharge the magnesium alloy blank, through the continuous effect of the pulse current, the flow stress of the magnesium alloy is significantly reduced by using the electropositive effect, the forming load is reduced, and the material is softened by using the Joule heat effect, the flowability and filling performance of the magnesium alloy blank are improved, so that the blank is more easily extruded and filled into the groove, and the forming precision of the component is improved; (2) Secondly, the rib end face forms a flow guide surface on both sides of the groove entrance, the two flow guide surfaces are inclined towards the groove direction respectively, the inner contour of the cavity of the blank is circular, the radius is R1, the outer contour of the rib end part is circular, the radius is R2, R1 is greater than R2, in the extrusion process, the rib end part first forms point contact when abutting against the cavity of the blank, the point contact forms a local high extrusion force, the force is concentrated, the extrusion resistance is reduced, and an initial deformation zone is formed, with the continuous feeding of the extrusion, line contact and surface contact are gradually formed between the two, the contact surface gradually expands, the flow direction of the blank tends to be consistent, the turbulence is reduced, and after the formation of surface contact extrusion, the compressive stress is uniform, and in the extrusion process, the continuous discharge effect of the pulse current is accompanied, the plastic effect of the pulse current on the magnesium alloy blank is maximized, at the same time, under the guidance of the flow guide surface, the blank is extruded into the groove, after the continuous extrusion of the blank into the groove, the blank first abuts against the back pressure area in the middle of the groove, the back pressure area generates back pressure on the blank after being extruded by the blank, at the same time, with the continuous expansion of the petal part, the blank continuously flows into the groove transversely, under the action of the back pressure and the radial extrusion force of the blank, the blank fills the groove on both sides transversely, effectively promoting the blank to flow towards both sides of the groove in the circumferential direction respectively, so that the blank is more easily filled in the groove; Further, the radial section of the groove is in the shape of a crescent, so that the blank can quickly fill both sides of the groove, greatly improving the forming precision of the component; (3) In addition, the rib end part is embedded with an electrode contact, the electrode contact protrudes from the rib end part, the pulse current device is connected to the electrode contact through a wire, which can locally discharge and soften the blank area covered by the rib on both sides of the groove before the rib abuts against the cavity of the blank, which can reduce the instantaneous resistance generated when the blank directly abuts against the male die, and the electrode contact is in the shape of a strip, which can discharge from point contact to line contact with the continuous feeding of the extrusion of the male die, which can promote the nucleation of recrystallized grains, with the expansion of the discharge area, more uniform Joule heat distribution is realized, the abnormal growth of grains is inhibited, and the plasticity of the magnesium alloy is improved. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is the structure diagram of the male die inserted into the cavity of the blank.

[0017] Figure 2This is a schematic diagram of the structure of the pulse current device of the present invention electrically connected to the punch and the die.

[0018] Figure 3 This is a schematic diagram of the magnesium alloy billet forming and demolding structure of the present invention.

[0019] Figure 4 This is a schematic diagram of the structure of the punch rib of the present invention.

[0020] Figure 5 This is a schematic diagram of the punch structure of the present invention.

[0021] Figure 6 yes Figure 5 A schematic diagram of the radial section of AA.

[0022] Figure 7 This is a schematic diagram of the radial cross-section of the flap abutting the inner cavity of the blank according to the present invention.

[0023] Figure 8 This is a schematic diagram of a longitudinal section of the middle part of the bottom wall of the magnesium alloy billet abutting groove of the present invention.

[0024] Figure 9 This is a comparison diagram of the extrusion molding effect of the present invention and the traditional extrusion molding effect.

[0025] Label Explanation 1-Die, 2-Punch, 3-Pulse current device, 4-Magnesium alloy blank, 5-Lobe, 6-Upper template, 7-Driver, 8-Die sleeve, 9-Rotating device, 10-Top plate, 11-Lower template, 12-Ejector rod, 14-Wire, 21-Rib, 22-Groove, 23-Guide surface, 24-Electrode contact, 41-Blank inner cavity, 42-Protruding rib, 51-Second inclined surface, 52-Left lobe, 53-Right lobe, 71-First inclined surface, 101-Cavity, 221-Outer arc, 222-Inner arc. Detailed Implementation

[0026] The invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] Unless otherwise expressly defined, the use of directional terms such as "center," "lateral," "longitudinal," "horizontal," "vertical," "top," "bottom," "inner," "outer," "upper," "lower," "front," "rear," "left," "right," "clockwise," and "counterclockwise" in the claims, description, and accompanying drawings of this invention is merely for the convenience of describing the invention and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the specific scope of protection of this invention.

[0028] likeFigures 1-9 As shown, the present invention provides an extrusion forming apparatus for a magnesium alloy thin-walled inner ring high-rib component, including a die 1, a punch 2, a pulse current device 3, an upper template 6, a drive component 7, a die sleeve 8, a rotating device 9, an ejection device and a lower template 11, and also includes a rotary extruder (not shown in the figure).

[0029] The magnesium alloy billet 4 is cylindrical with a central cavity 41. The die 1 forms a cavity 101 with a top-side opening. The cavity 101 has an annular structure, and its inner contour is consistent with the outer contour of the magnesium alloy billet 4. The cavity 101 allows the magnesium alloy billet 4 to be inserted downwards. The punch 2 is located directly above the cavity 101 and can move up and down. After the magnesium alloy billet 4 is inserted into the cavity 101, the punch 2 can descend and insert into the inner cavity 41 of the billet, or rise and exit the inner cavity 41 of the billet. Specifically, the punch 2 is connected to the bottom of the rotary extruder through a sliding component (not shown in the figure). The rotary extruder drives the punch 2 to move up and down and can control the punch 2 to descend to different heights to align with different heights of the inner cavity 41 of the billet. The rotary extruder is an existing rotary hydraulic press.

[0030] Key points combined Figure 1 As shown, the sidewall of the punch 2 has multiple ribs 21 protruding laterally. These ribs 21 are longitudinally spaced, forming grooves 22 between adjacent ribs 21. After the punch 2 is inserted into the blank cavity 41, the ribs 21 compress the inner wall of the blank cavity 41, causing the magnesium alloy blank 4 to radially fill the grooves 22. The punch 2 is composed of multiple segments 5, all of which are identical fan-shaped structures. These segments 5 are arranged in a circumferential array around the longitudinal axis of the punch 2, allowing them to expand radially away from each other or approach each other radially. When radially away, each segment 5 approaches the inner wall of the blank cavity 41 and compresses it. When radially approaching, each segment 5 closes to form an annular punch 2. Specifically, the multiple segments 5 include a left segment 52 and a right segment 53 symmetrically arranged. The moving part 7 is located between the left lobe 52 and the right lobe 53. The driving part 7 extends longitudinally, and the longitudinal axis of the driving part 7 coincides with the longitudinal axis of the punch 2. The driving part 7 has a columnar structure, and the bottom side is inclined downward and inward to form a cone shape, forming a first inclined surface 71. The lobe 5 is provided with a second inclined surface 51 that fits against the first inclined surface 71 on the side facing the driving part 7. The top of the driving part 7 is connected to the ejector cylinder of the rotary extruder (not shown in the figure). The ejector cylinder drives the driving part 7 to move up and down axially. During the descent of the driving part 7, the first inclined surface 71 pushes down against the second inclined surface 51, causing each lobe 5 to radially move away from the outward expansion. The radial outward expansion distance of the lobe 5 is controlled by the descent height of the driving part 7. When the driving part 7 rises and resets, the sliding component drives the left lobe 52 and the right lobe 53 to radially approach and close.

[0031] In this specific embodiment, the upper template 6 is fixedly installed below the rotary extruder. The sliding assembly includes a pair of slide rails and a pair of connecting keys. The pair of slide rails are distributed on both sides below the upper template 6 along the axis of the punch 2. The pair of connecting keys are slidably engaged on the slide rails. The other ends are fixed to the left lobe 52 and the right lobe 53, respectively. A return spring (not shown in the figure) is provided between the connecting key and the upper template 6. The return spring is used to limit the connecting key to move radially outward along the slide rail. This is prior art and will not be described in detail. The upper template 6 has a first through hole in the longitudinal direction. The top end of the drive member 7 passes through the through hole and is connected to the ejector cylinder (not shown in the figure). The rotary extruder drives the upper template 6, punch 2, drive member 7 and ejector cylinder to rise or fall as a whole. The ejector cylinder independently drives the drive member 7 to rise and fall relative to the punch 2.

[0032] The rotating device 9 is rotatably mounted on the lower template 11 and fixedly connected to the bottom side of the die 1. The die sleeve 8 is cylindrical. The die 1 is embedded in the die sleeve 8 and fixedly connected to the die sleeve 8, so that the die sleeve 8 and the die 1 are installed and fixed as a whole on the rotating device 9. As the rotating device 9 rotates horizontally, the rib 21 can rotate and press the inner wall of the blank cavity 41 at different positions along the circumferential direction, so as to form a ring-shaped rib 42 that bulges radially on the inner wall of the blank cavity 41. Key points such as Figure 3 As shown, the ejection device includes a top plate 10, an ejector rod 12, and a lifting drive mechanism (not shown in the figure). The top plate 10 is slidably disposed in the cavity 101 to eject the magnesium alloy billet 4 upward. One end of the ejector rod 12 is connected to the bottom side of the top plate 10, and the other end is connected to the telescopic end of the lifting drive mechanism. A second through hole is longitudinally penetrating on the lower template 11. The top end of the ejector rod 12 passes upward through the second through hole and is fixedly connected to the bottom side of the top plate 10. The lifting drive mechanism can be a lifting cylinder connected to the bottom end of the ejector rod to drive the ejector rod 12 to move up and down.

[0033] Key points combined Figure 2 As shown, the cathode and anode of the pulse current device 3 are electrically connected to the punch 2 and the die 1, respectively, so that the punch 2, the magnesium alloy billet 4, the die 1 and the pulse current device 3 are sequentially connected to form a current circuit, so that when the rib 21 abuts against the magnesium alloy billet 4, the rib 21 can partially discharge the magnesium alloy billet 4. Preferably, the peak current density of the pulse current is 100 to 250 A / mm², and the pulse frequency is 100 to 500 Hz.

[0034] Key points combined Figure 2As shown, to ensure that the current flows effectively through the magnesium alloy billet 4, insulating gaskets (not shown in the figure) are provided between the left lobe 52 and the right lobe 53 and the upper template 6, insulating gaskets are provided between the left lobe 52 and the right lobe 53 and the driving component 7, insulating gaskets are provided between the die 1 and the die sleeve 8, and insulating gaskets are provided between the die 1 and the rotating device 9. The insulating gaskets are used for electrical insulation. These insulating gaskets effectively isolate the conductive path between the punch 2 and the upper template 6 and the driving component 7, as well as between the die 1 and the rotating device 9 and the lower template 11, so that the current is sequentially conducted through the punch 2, the magnesium alloy billet 4, the die 1 and the pulse current device 3 to form a current loop.

[0035] Key points combined Figure 4 As shown, the end faces of two adjacent ribs 21 form guide surfaces 23 on both sides of the inlet of the groove 22. The two guide surfaces 23 are inclined towards the groove 22, and the bottom side of the guide surface 23 transitions with the groove 22 to form an arc angle r (e.g., Figure 5 As shown), to reduce the resistance to the flow of the billet, specifically, there are two ribs 21, and a groove 22 is formed between the two ribs 21. Preferably, the included angle α between the guide surfaces 23 on both sides of the inlet of the groove 22 is 135° to 145°.

[0036] Key points combined Figures 6-7 As shown, the cross-sectional profile of the bottom wall of the groove 22 is arc-shaped, the punch 2 extends longitudinally, the cross-section of the groove 22 is a radial section, and the middle of the bottom wall of the groove 22 bulges towards the end of the rib 21, forming a back pressure zone. The two sides of the bottom wall of the groove 22 move away from the end of the rib 21. When the magnesium alloy billet 4 is squeezed into and abuts against the back pressure zone, it is subjected to the back pressure of the back pressure zone. At this time, the side wall of the punch 2 is separated from the inner wall of the inner cavity 41 of the billet, and the separation is represented by d (e.g., Figure 8 As shown), multiple lobes 5 can continuously expand outward, allowing the magnesium alloy billet 4 to continuously flow into the groove 22 and flow towards both sides of the bottom wall of the groove 22, forming a transverse extrusion force on the magnesium alloy billet 4 in the groove 22. Under the action of back pressure and transverse extrusion force, the magnesium alloy billet 4 in the groove 22 flows freely, promoting the billet to flow towards both sides of the groove 22 in the circumferential direction, gradually filling the groove 22.

[0037] Preferably, the inner contour of the blank cavity 41 is circular with a radius of R1, and the outer contour of the rib 21 is an arc with a radius of R2. Figure 7 As shown, R1 is greater than R2, and the end of the rib 21 is inclined to form the guide surface 23. When the punch 2 contacts and extrudes the inner cavity 41 of the blank laterally, the extrusion surface between the rib 21 and the inner cavity 41 of the blank gradually increases, first forming point contact, and then forming line contact and surface contact, effectively improving the extrusion effect and promoting the flow of magnesium alloy blank 4.

[0038] Preferably, the cross-section of the groove 22 is a crescent-shaped structure. After the magnesium alloy billet 4 flows into the groove 22, it is easier to fill both sides of the groove 22 when it flows towards both sides of the groove 22, effectively improving the forming accuracy of the component. The crescent-shaped cross-section has an outer arc 221 and an inner arc 222. The curvature of the outer arc 221 is greater than that of the inner arc 222, and the eccentricity between the two is n, where eccentricity n = Δb, and Δb is the total radial feed amount, that is, the radial extrusion feed amount after the rib 21 abuts against the inner cavity 41 of the billet. The inner arc 222 is the bottom wall of the groove 22, and the radius of the inner arc is R0, where R0 is less than R1, and R1 > R2 > R0.

[0039] Preferably, an electrode contact 24 is embedded at the end of the rib 21. The electrode contact 24 is strip-shaped and extends circumferentially along the end of the rib 21. The electrode contact 24 protrudes from the end of the rib 21. The pulse current device 3 is connected to the electrode contact 24 through a wire so that before the punch 2 extrudes the inner cavity 41 of the blank, the pulse current is focused through the electrode contact 24 onto the area to be formed on the inner wall of the inner cavity 41 of the blank, forming a local high-density current path. The electrode contact 24 is made of one of gold, silver, copper, or aluminum materials, which has high conductivity and strong stability.

[0040] In this specific embodiment, the key points are as follows: Figure 4 As shown, the height of groove 22 is the working height m, and the depth of groove 22 is the real-time rib thickness h. The working height m is dynamically adjusted according to the real-time rib thickness h. When h < 30mm, m = (3.5~3.7) × h; when 30mm < h < 60mm, m = (2.4~2.5) × h; when h > 60mm, m = (1.8~2.0) × h; the arc angle r is between 14 and 18mm.

[0041] Key points combined Figure 9 As shown in the figure, the left side illustrates the cross-sectional results of the ribs under rotary extrusion forming with and without pulsed current. Without current, the rib height is significantly lower than the design value, the rib top shows obvious collapse or depression, the rib wall joint has an indistinct outline, and there are defects such as incomplete filling. Figure 9 As shown in the enlarged left image, after current is applied, as... Figure 9 As shown in the enlarged view on the right, the groove 22 is completely and densely filled, and the forming ribs are precisely up to the design value, with no visible defects such as incomplete filling or folds.

[0042] In this specific embodiment, the punch 2 is made of copper-tungsten alloy, and the die 1 is made of steel.

[0043] The present invention also provides a method for rotary extrusion forming of a magnesium alloy thin-walled inner ring high-rib member, comprising the following steps: Step 1, Pre-forming preparation: The magnesium alloy blank 4 to be formed is embedded into the cavity 101. The multiple segments 5 of the punch 2 are connected to the cathode of the pulse current device 3 through wires 14. The die 1 is connected to the anode of the pulse current device 3 through wires 14. The pulse current device 3 is energized. Step 2, Height Positioning: The punch 2 descends to the predetermined height and is inserted into the blank cavity 41; Step 3, extrusion forming: Multiple petals 5 expand radially outward and abut against the inner wall of the blank cavity 41, forming a current loop. The pulse current partially discharges the magnesium alloy blank 4 at the abutment point. Multiple petals 5 continue to expand outward, and the ribs 21 extrude the blank cavity 41. The magnesium alloy blank 4 flows into the groove 22 along the guide surface 23. When the magnesium alloy blank 4 abuts against the middle of the bottom wall of the groove 22, the side wall of the punch 2 is spaced from the inner wall of the blank cavity 41. Multiple petals 5 continue to expand outward until the side wall of the punch 2 abuts against the inner wall of the blank cavity 41. The magnesium alloy blank 4 flows circumferentially towards both sides of the bottom wall of the groove 22, horizontally filling the groove 22 and gradually filling the groove 22. Step 4, Rotary extrusion forming: The rotating device 9 drives the die 1 to rotate horizontally to different angles and continuously applies pulse current. The ribs 21 extrude different areas to be formed at the same height in the inner cavity 41 of the blank until the inner wall of the inner cavity 41 of the blank at the predetermined height is extruded to form a ring-shaped annular rib 42. Step 5: Unload the material, turn off the pulse current, multiple petals 5 move laterally closer together and rise out of the blank cavity 41, and remove the formed component.

[0044] Furthermore, after step 4 is completed, steps 2 to 4 are repeated to lower the punch 2 to different heights and press the inner wall of the blank cavity 41 at different heights to form multiple longitudinally spaced annular ribs 42.

[0045] In step 4, before each rotation of the rotating device 9, the multiple petals 5 first move laterally closer together so that the ribs 21 only keep in contact with the inner cavity 41 of the blank, so that the pulse current can be continuously supplied. After the rotating device 9 rotates, step 3 is repeated.

[0046] The forming device also includes a top plate 10, which is slidably disposed in the cavity 101. In step 1, the magnesium alloy blank 4 is placed on the top surface of the top plate 10. In step 4, the top plate 10 slides upward to push the forming component out of the cavity 101, completing the demolding. Finally, the next magnesium alloy blank 4 to be formed is re-embedded into the cavity 101 for the extrusion forming of the next forming component.

[0047] The present invention has the following advantages over the traditional extrusion method for integrated magnesium alloy thin-walled high-strength components: (1) Improve the fluidity of the billet: By passing a pulse current through the magnesium alloy billet 4, the extrusion point is partially discharged, which improves the fluidity and filling performance of the magnesium alloy billet 4, making it easier for the billet to be extruded and fill the groove 22. (2) Reduce the extrusion resistance of the die: When the punch 2 is closed, the outer diameter is smaller than the inner diameter of the blank cavity 41. During extrusion, point contact is formed, which can form local high extrusion pressure, concentrate the force, reduce the extrusion resistance, form the initial deformation zone, reduce the extrusion resistance, and at the same time, the continuous action of the pulse current is always maintained to maintain the fluidity of the magnesium alloy blank 4 in the extrusion zone, further reducing the extrusion resistance. (3) Improve filling accuracy: The radial section of the groove 22 is a crescent-shaped structure and the bottom wall of the groove 22 is an inner arc 222. When the magnesium alloy billet 4 first comes into contact with the inner arc 222, it can form a back pressure on the magnesium alloy billet 4. Under the action of the transverse extrusion force generated by the continuous transverse flow of the billet, the magnesium alloy billet 4 is promoted to flow along the circumferential direction towards the two sides of the inner arc 222, filling the groove 22 and improving the forming accuracy. (4) Protect the mold: After one extrusion is completed, while maintaining contact with the inner cavity 41 of the blank, move each petal 5 laterally closer to the inner cavity 41 of the blank to avoid the petal 5 being subjected to circumferential extrusion force when the die 1 rotates, thereby reducing wear. When the die 1 rotates to the predetermined angle, each petal 5 will again laterally extrude the inner wall of the inner cavity 41 of the blank, ensuring the extrusion effect while extending the service life of the mold.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the design of this case. All equivalent changes made based on the key design features of this case shall fall within the protection scope of this case.

Claims

1. An extrusion forming apparatus for a magnesium alloy thin-walled inner ring high-rib member, characterized in that: Includes a concave die (1), a convex die (2), and a pulse current device (3). The magnesium alloy billet (4) is cylindrical with a central cavity (41). The die (1) forms a cavity (101) with a top side opening, and the cavity (101) allows the magnesium alloy blank (4) to be inserted downwards; The punch (2) is located directly above the cavity (101) and can move up and down. After the magnesium alloy blank (4) is inserted into the cavity (101), the punch (2) can descend to insert into the inner cavity (41) of the blank and rise to exit the inner cavity (41) of the blank. The sidewall of the punch (2) has multiple ribs (21) that are laterally protruding. The multiple ribs (21) are longitudinally spaced and form a groove (22) between adjacent ribs (21). The punch (2) is composed of multiple petals (5). Each petal (5) can expand laterally away from the outside so that after the punch (2) is inserted into the inner cavity (41) of the blank, the inner wall of the inner cavity (41) of the blank is squeezed by the ribs (21) so that the magnesium alloy blank (4) fills the groove (22). The cathode and anode of the pulse current device (3) are electrically connected to the punch (2) and the die (1) respectively, so that the punch (2), the magnesium alloy billet (4), the die (1) and the pulse current device (3) are sequentially connected to form a current circuit, so that when the rib (21) abuts against the magnesium alloy billet (4), the rib (21) can partially discharge the magnesium alloy billet (4).

2. The extrusion forming apparatus for a magnesium alloy thin-walled inner ring high-rib member as described in claim 1, characterized in that: The end faces of the two adjacent ribs (21) form guide surfaces (23) on both sides of the inlet of the groove (22), and the two guide surfaces (23) are inclined towards the groove (22).

3. The extrusion forming apparatus for a magnesium alloy thin-walled inner ring high-rib member as described in claim 2, characterized in that: The included angle between the guide surfaces (23) on both sides of the inlet of the groove (22) is 135° to 145°.

4. The extrusion forming apparatus for a magnesium alloy thin-walled inner ring high-rib member as described in claim 1, characterized in that: The cross-sectional profile of the bottom wall of the groove (22) is arc-shaped, and the middle part of the bottom wall bulges towards the end of the rib (21) to form a back pressure zone. The two sides of the bottom wall extend away from the end of the rib (21).

5. The extrusion forming apparatus for a magnesium alloy thin-walled inner ring high-rib member as described in claim 4, characterized in that: The cross-section of the groove (22) is crescent-shaped.

6. The extrusion forming apparatus for a magnesium alloy thin-walled inner ring high-rib member as described in claim 1, characterized in that: The inner contour of the blank cavity (41) is circular with a radius of R1, and the outer contour of the end of the rib (21) is arc-shaped with a radius of R2, where R1 is greater than R2.

7. The extrusion forming apparatus for a magnesium alloy thin-walled inner ring high-rib member as described in claim 1, characterized in that: The end of the rib (21) is provided with an electrode contact (24). The electrode contact (24) is strip-shaped and extends circumferentially along the end of the rib (21). The electrode contact (24) protrudes from the end of the rib (21). The pulse current device (3) is connected to the electrode contact (24) through a wire. Before the punch (2) extrudes the inner cavity (41) of the blank, the electrode contact (24) partially discharges the magnesium alloy blank (4).

8. The extrusion forming apparatus for a magnesium alloy thin-walled inner ring high-rib member as described in claim 1, characterized in that: The concave die (1) can rotate horizontally, so that the punch (2) can press the inner wall of the blank cavity (41) at different positions to form annular ribs (42).

9. The extrusion forming apparatus for a magnesium alloy thin-walled inner ring high-rib member as described in claim 1, characterized in that: It also includes an upper template (6) and a driving component (7). Multiple petals (5) are radially slidably disposed on the bottom side of the upper template (6) via a sliding component. The driving component (7) is disposed between the multiple petals (5) and moves up and down relative to the multiple petals (5). The driving component (7) is cylindrical, with its bottom inclined downward and concave inward to form a first inclined surface (71). The multiple petals (5) form a second inclined surface (51) that fits against the first inclined surface (71) on the side facing the driving component (7). When the driving component (7) descends, it drives each petal (5) to simultaneously move radially away from the outside. When the driving component (7) rises, the sliding component drives each petal (5) to move radially closer and close together. An insulating element is provided between each petal (5) and the upper template (6), and an insulating element is provided between each petal (5) and the driving element (7).

10. The extrusion forming apparatus for a magnesium alloy thin-walled inner ring high-rib member as described in claim 1, characterized in that: The punch (2) is made of copper-tungsten alloy, and the die (1) is made of steel.

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