A hot stretching forming device applicable to forming a spherical surface on a flat plate

Abstract

This application relates to the technical field of sheet metal forming processes, and specifically discloses a hot stretch forming device applicable to forming a spherical surface from a flat plate, including a blank holder for fixing the sheet and preventing the sheet from wrinkling during the stretching process, and a female die and a male die for the stretching process. The blank holder is a slidable circular ring, and a raised bead is provided on the top surface of the blank holder. The top surface of the blank holder inside the bead is a flat surface, and a ring groove that can cooperate with the bead is provided on the outer periphery of the bottom surface of the female die. The purpose of this patent is to solve the problem that after the part is stretched, a fixture is required to position and cut the part, and the fixture cost is relatively high, which affects the cutting cost of the part.

Description

Technical Field

[0001] The present invention relates to the technical field of sheet metal forming processes, and particularly to a hot stretching forming device suitable for forming a spherical surface from a flat plate. Background Art

[0002] Drawing, also known as stretching, drawing, rolling, etc., refers to a machining process in which a flat blank of a certain shape obtained after blanking is stamped into various open hollow parts by using a mold, or the diameter of an open hollow blank is reduced and the height is increased. Sheet metal parts with thin walls of cylindrical, stepped, conical, spherical, box-shaped and other irregular shapes can be manufactured by the stretching process. In cooperation with other stamping forming processes such as flanging, bulging, flaring, necking, etc., parts with extremely complex shapes can also be manufactured. Therefore, the stretching process plays a very important role in the production processes of industrial sectors such as automobiles, airplanes, tractors, electrical appliances, instruments, and electronics.

[0003] When the sheet metal is stretched, the tangential compressive stress in the flange part is so large that it exceeds the anti-instability ability of the material, and the material in the flange part will become unstable and bulge. This phenomenon is called wrinkling. At present, in order to solve this wrinkling phenomenon, a blank holder is usually used. Through the action of the blank holding force of the blank holder, the blank is not easily arched to achieve the purpose of anti-wrinkling. However, after the sheet metal is stretched, a customized positioning fixture is usually required to position the stretched part. The part is placed on the fixture, and the cutting equipment positions the part to be cut. In order to avoid cutting errors, the cutting equipment only needs to cut at the positioning place where the part is placed on the fixture. However, the positioning fixture needs to be designed separately according to the structure of the part, which greatly increases the production cost of the part. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a hot stretching forming device suitable for forming a spherical surface from a flat plate, which solves the problem that after the part is stretched, a fixture is required to position and cut the part, and the cost of the fixture is relatively high, affecting the cutting cost of the part.

[0005] In order to solve the above problems, the technical solution adopted by the present invention is:

[0006] A hot stretching forming device suitable for forming a spherical surface from a flat plate includes a blank holder for fixing the sheet metal and preventing the sheet metal from wrinkling during the stretching process, and a female die and a male die for the stretching process. The blank holder is a slidable circular ring, and there are raised drawing beads on the top surface of the blank holder. The top surface of the blank holder inside the drawing beads is a plane, and there is an annular groove on the bottom surface of the female die that can cooperate with the drawing beads.

[0007] The principle of this solution is:

[0008] When stretch-forming a sheet metal, place the sheet metal to be stretched on the punch and the blank holder. At this time, the die moves downward to extrude the sheet metal. Under the action of the draw bead and the annular groove, the sheet metal forms a bulge. The bulged part of the sheet metal can be firmly fixed between the punch and the die. After the sheet metal is fixed, then the punch and the blank holder move downward synchronously to stretch-form the fixed sheet metal. After the sheet metal is extruded and formed, lift the die upward and lift the blank holder upward. At this time, the stretching of the sheet metal is completed.

[0009] The beneficial effects produced by this solution are:

[0010] In the solution of this application, since the thickness of the part continuously thins during the stretching process, by setting the draw bead and the annular groove, it is possible to fix the periphery of the sheet metal, so that when the middle part of the sheet metal is stretched, the material feeding of the sheet metal can be uniform, thereby ensuring the consistency of the wall thickness of the part; secondly, due to the existence of the draw bead, a bulge will be formed on the flange of the part during the stretching process. When cutting the redundant outer periphery of the part, there is no need to use a special fixture to clamp and position the part. Only need to manually cut along the outer periphery of the bulge of the part with a cutting device, which is convenient for the cutting device to cut the part and reduces the processing cost of the part; finally, during the long-term use of the machine tool, the surface of the punch in contact with the sheet metal will wear, and it is difficult to ensure the pressing force between the blank holder and the die. The effect of simply using the blank holder to prevent the part from wrinkling will be reduced. However, using the draw bead can form a bulge on the outer periphery of the sheet metal and press and fix the sheet metal under the pressure of the die, so that the sheet metal always remains fixed during the stretching process.

[0011] Furthermore, the bottom end of the punch is connected with a disc-shaped bottom plate through screws. A through hole is vertically opened on the outer periphery of the bottom plate, and the through holes are evenly distributed on the outer periphery of the bottom plate. A push rod for pushing the blank holder to slide up and down is threaded through the through holes. After a bulge is formed on the edge of the sheet metal, the die and the push rod move downward synchronously to stretch-form the sheet metal; and after the part is processed, the part adheres tightly to the punch. At this time, it is necessary to remove the die from the upper part of the part. The push rod rises, pushes the blank holder upward, and separates the part from the die, which is convenient for removing the part.

[0012] Furthermore, threaded holes are opened on the outer peripheral sides of the bottom plate, the blank holder and the die, and lifting eye bolts are connected in the threaded holes. By setting the lifting eye bolts, the bottom plate, the blank holder and the die can be lifted by a hoisting device installed on a gantry crane, which is convenient for the movement of the bottom plate, the blank holder and the die.

[0013] Furthermore, a main cylinder for pushing the female mold to move is arranged above the female mold. At the same time, a through hole for exhausting air is vertically opened at the center of the top end surface of the female mold. The output end of the main cylinder is in close contact with the top surface of the female mold. The output end of the main cylinder drives the female mold to move, so as to control the extrusion force of the female mold on the part, avoiding the situation that the extrusion force is too small and the part is not formed in place. A through hole for exhausting air is vertically opened at the center of the top end surface of the female mold. The through hole at the top of the female mold can discharge the compressed gas when the female mold extrudes the plate.

[0014] Furthermore, a lifting hole is opened at the center of the punch. After the part is formed, by connecting a lifting screw in the lifting hole, the punch can be lifted by the lifting equipment on the gantry crane, and the lifting hole will not affect the part during the stretching process.

[0015] Furthermore, a "T-shaped" hydraulic groove is provided inside the bottom plate and the punch. The hydraulic groove is filled with hydraulic oil. The bottom end of the hydraulic groove is connected to an auxiliary cylinder. Two sliding components are respectively and slidably connected to both sides of the inner top end of the hydraulic groove. The sliding components are slidably and hermetically connected to the hydraulic groove. The sliding components are composed of two oppositely arranged push plates, and the two oppositely arranged push plates are fixedly connected by a rod.

[0016] Furthermore, retractable positioning beads are installed at the tops of the push rods on the left and right sides of the bottom plate. A pressing switch for controlling the start of the auxiliary cylinder is installed at the bottom end of the positioning beads. When the push rod rises to push the blank holder to move, the positioning beads contract. When the positioning beads contract into the push rod, the positioning beads will press against the pressing switch, the pressing switch is activated, the auxiliary cylinder is activated, and part of the hydraulic oil in the hydraulic groove is pushed out of the hydraulic groove. The hydraulic oil will push the sliding device to move along the hydraulic groove towards the middle of the punch.

[0017] Furthermore, through grooves are respectively and horizontally opened on the left and right sides inside the blank holder. Clamping blocks that can slide horizontally are placed in the through grooves. One side of the clamping block facing the punch is wedge-shaped. A spring is connected to the side of the clamping block away from the punch. One end of the spring is fixed to the clamping block, and the other end is fixed to the inner side wall of the through groove opened on the blank holder. Since the blank holder needs to be lifted first when stretching the plate, so that the top surface of the blank holder is in the same plane as the top surface of the punch. At this time, the clamping block will extend into the hydraulic groove outside the push plate under the action of the spring. At this time, under the action of the clamping block, the blank holder and the punch are in a connected state. At this time, the female mold can extrude the plate, and under the action of the draw bead, an annular protrusion for fixing the plate is pressed out.

[0018] Further, U-shaped rods are installed on the left and right sides of the blank holder. The middle part of the U-shaped rod is rotatably connected to a cross bar protruding from the side wall of the blank holder. A torsion spring is provided on the U-shaped rod. One end of the U-shaped rod is inserted into a through groove on the side of the blank holder, and one end of the U-shaped rod is in contact with the side of the clamping block away from the punch. At the same time, the other end of the U-shaped rod is inserted into a limit groove provided on the side of the die. The limit grooves are respectively opened on the bottom side of the die. After an annular protrusion is extruded on the surface of the sheet material, it is necessary for the die to drive the blank holder to move downward to complete the stretching operation of the sheet metal part. By clamping the two ends of the U-shaped rod in the limit groove on the side of the die and the through groove on the side of the blank holder respectively, the connection between the die and the blank holder is completed, so that the die can move downward simultaneously with the blank holder, and there is no need for the push rod to move downward synchronously with the die. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of the present invention;

[0020] Figure 2 is a top view schematic diagram of the present invention;

[0021] Figure 3 is the present invention Figure 2 schematic diagram of the (A-A) section in;

[0022] Figure 4 is a schematic diagram of the bottom plate of the present invention;

[0023] Figure 5 is a schematic diagram of the punch of the present invention;

[0024] Figure 6 is a schematic diagram of the blank holder of the present invention;

[0025] Figure 7 is a schematic diagram of the die of the present invention;

[0026] Figure 8 is a schematic diagram of the annular groove of the pressing die of the present invention;

[0027] Figure 9 is a schematic diagram of the sheet material in a stretched and formed state of the present invention;

[0028] Figure 10 is a schematic diagram of the final state of the part of the present invention;

[0029] Figure 11 is a schematic diagram of the second embodiment of the present invention;

[0030] Figure 12 is the present invention Figure 11 magnified schematic diagram at A in.

[0031] The reference numerals in the drawings of the specification include:

[0032] Bottom plate 1, blank holder 2, draw bead 2-1, punch 3, lifting hole 3-1, die 4, annular groove 4-1, push rod 5, positioning bead 5-1, push button switch 5-2, hydraulic groove 6, push plate 7, rod 7-1, clamping block 8, spring 9, U-shaped rod 10, torsion spring 11, limit groove 12. Detailed implementation mode

[0033] The following is a further detailed description through specific implementation modes:

[0034] Take the attached Figure 1 as an example. In the attached drawing, the bottom plate 1 is arranged at the bottom of the punch 3, taking this as the direction reference.

[0035] The first embodiment is basically as shown in the attached Figures 1 to 10 drawing:

[0036] There is a kind of part in the aircraft that is formed by the stretching process. The titanium alloy sheet is placed in an environment with a temperature of 730 °C for stretching and forming. The sheet is placed on the top surface of the cylindrical punch 3. The punch 3 is as shown in the attached Figure 5 drawing. At the bottom of the punch 3, a disc-shaped bottom plate 1 is connected by an M16*40 hexagon socket head cap screw. The bottom plate 1 is as shown in the attached Figure 4 drawing. Through holes are vertically opened on the surface of the bottom plate 1, and the through holes are evenly distributed circumferentially along the center of the bottom plate 1. The bottom plate 1 is placed on the machine tool. At the same time, a plurality of push rods 5 that can protrude upward are vertically arranged on the machine tool, and the push rods 5 pass through the through holes evenly distributed on the surface of the bottom plate 1.

[0037] A slidable blank holder 2 is sleeved on the outer periphery of the punch 3. The blank holder 2 is circular ring-shaped. The blank holder 2 is as shown in the attached Figure 6 drawing. A ring-shaped draw bead 2-1 is arranged on the top surface of the blank holder 2. The top of the blank holder 2 is a plane. When stretching the sheet, the push rod 5 jacks up the blank holder 2 to make the top surface of the blank holder 2 and the top surface of the punch 3 in the same plane. Then the sheet is placed on the punch 3 and the blank holder 2. The die 4 moves downward. The sheet is squeezed by the die 4 and forms a protrusion under the action of the draw bead 2-1. At this time, the fixing of the sheet is completed. After the sheet is fixed, the punch 3 and the push rod 5 move downward synchronously to stretch the sheet. The planes on both sides of the draw bead 2-1 can ensure that the sheet will not wrinkle during the stretching process. Secondly, the protruding draw bead 2-1 can ensure that the sheet feeds evenly during the stretching process and avoid the situation that the wall thickness of the stretched part is inconsistent.

[0038] After the part is stretched and formed, the part is tightly attached to the punch 3. At this time, the push rod 5 rises to jack up the blank holder 2 to separate the part from the punch 3, facilitating the removal of the stretched part.

[0039] The die 4 is placed on the upper part of the punch 3. The die 4 is as shown in the attachedFigures 7 to 8 As shown, the bottom end face of the female die 4 is fitted with the top face of the male die 3. A ring groove 4-1 that can cooperate with the draw bead 2-1 is provided on the bottom face of the female die 4. By providing the ring groove 4-1 and the draw bead 2-1, an upwardly bulging annular structure can be formed on the outer periphery of the sheet metal. At this time, the sheet metal is in a fixed state between the female die 4 and the male die 3. After the part is stretched, a cutting process is required. At this time, the stretched part does not need to be positioned using a specially customized fixture. The inner planar part of the bulging part is directly cut off by a cutting tool. The state of the part after stretching and forming is as shown in the appendix Figure 9 As shown, after the outer periphery of the part is cut, the part is placed in a five-axis laser cutting device, and the top face of the part is cut to form an opening. The state of the part after cutting is as shown in the appendix Figure 10 shown

[0040] A through hole that penetrates radially is provided at the center of the top face of the female die 4. This through hole is used for exhausting air during the process of extruding the part. At the same time, a main cylinder is connected above the female die 4. The main cylinder is a hydraulic cylinder, and the output end of the main cylinder abuts against the top face of the female die 4. The main cylinder and the push rod 5 drive the female die 4 to move towards the bottom plate 1 synchronously, and the sheet metal placed on the top face of the male die 3 is stretched and formed

[0041] Holes are provided on the outer peripheral side walls of the bottom plate 1, the blank holder 2, and the female die 4. A lifting eye bolt of model M12 can be placed in the holes. A gantry crane is installed in the site environment of the stretching process, and a lifting tool is installed on the gantry crane. The lifting tool can lift the bottom plate 1, the blank holder 2, and the female die 4 through the lifting eye bolts for position transfer, which is convenient for stretching the sheet metal in different sites. Secondly, a lifting hole 3-1 is provided at the center of the top face of the male die 3. During lifting, a lifting bolt can be installed in the lifting hole 3-1 to lift and disassemble the male die 3

[0042] The specific implementation process of Embodiment 1 is as follows

[0043] When it is necessary to stretch the sheet metal into a part, the main cylinder is started at this time. The main cylinder drives the female die 4 to move upward, exposing the male die 3. Then the push rod 5 is started, and the push rod 5 rises to lift the blank holder 2. At this time, the top faces of the blank holder 2 and the male die 3 are in the same plane. Then the sheet metal to be processed is placed on the male die 3 and the blank holder 2. The main cylinder is started, and the main cylinder drives the female die 4 to move downward, squeezing the outer periphery of the sheet metal at the draw bead 2-1 to form a bulge and fixing it. The main cylinder and the push rod 5 move downward synchronously to stretch the middle part of the sheet metal. When the bottom face of the blank holder 2 is in contact with the bottom plate 1, the processing of the sheet metal to form a product is completed. Finally, the main cylinder drives the female die 4 to move upward, and the push rod 5 pushes the blank holder 2 upward, and the processed part can be taken out

[0044] Embodiment 2 is as shown in the appendix Figures 11 to 12As shown, the difference between the second embodiment and the first embodiment described above is that a "T-shaped" hydraulic groove 6 for storing hydraulic oil is provided in the middle of the bottom plate 1 and the punch 3. The bottom end of the hydraulic groove 6 is connected to an auxiliary cylinder, and the auxiliary cylinder is a hydraulic cylinder, which is not shown in the drawings. On the left and right sides of the inner top of the hydraulic groove 6, sliding components capable of horizontal sliding are respectively placed, and the sliding components are slidably and sealingly connected to the inner wall of the hydraulic groove 6; the sliding components are composed of two oppositely arranged push plates 7, and a rod 7-1 is used to connect the two oppositely arranged push plates 7.

[0045] At the top of the push rods 5 on the left and right sides of the bottom plate 1, retractable positioning beads 5-1 are installed. At the bottom end of the positioning beads 5-1, a push button switch 5-2 for controlling the start of the auxiliary cylinder is installed. When the push rod 5 rises to push the blank holder 2 to move, the positioning bead 5-1 contracts. When the positioning bead 5-1 contracts into the push rod 5, the positioning bead 5-1 will squeeze the push button switch 5-2, the push button switch 5-2 is activated, the auxiliary cylinder is activated, and part of the hydraulic oil in the hydraulic groove 6 is pushed out of the hydraulic groove 6, and the hydraulic oil will push the sliding device to move along the hydraulic groove 6 towards the middle of the punch 3.

[0046] On the left and right sides of the blank holder 2, through grooves are respectively opened horizontally. In the through grooves, clamping blocks 8 that can slide horizontally are placed. One side of the clamping block 8 facing the punch 3 is wedge-shaped. On the side of the clamping block 8 away from the punch 3, a spring 9 is connected. One end of the spring 9 is fixed to the clamping block 8, and the other end is fixed to the inner side wall of the through groove opened on the blank holder 2. Since the blank holder 2 needs to be lifted first when stretching the sheet material, so that the top surface of the blank holder 2 is in the same plane as the top surface of the punch 3. At this time, the clamping block 8 will extend into the hydraulic groove 6 outside the push plate 7 under the action of the spring 9. At this time, under the action of the clamping block 8, the blank holder 2 and the punch 3 are in a connected state. At this time, the die 4 can extrude the sheet material, and under the action of the draw bead 2-1, an annular protrusion for fixing the sheet material is pressed out.

[0047] U-shaped rods 10 are installed on the left and right sides of the blank holder 2. The middle part of the U-shaped rod 10 is rotationally connected to the crossbar protruding from the side wall of the blank holder 2. A torsion spring 11 is arranged on the U-shaped rod 10. One end of the U-shaped rod 10 is clamped into the through groove on the side of the blank holder 2, and one end of the U-shaped rod 10 is in contact with the side of the clamping block 8 away from the punch 3. At the same time, the other end of the U-shaped rod 10 is clamped into the limit groove 12 arranged on the side of the die 4. The limit grooves 12 are respectively opened on the bottom side of the die 4. After extruding an annular protrusion on the surface of the sheet, it is necessary for the die 4 to drive the blank holder 2 to move downward to complete the stretching operation of the sheet. At this time, the push rod 5 moves downward, the positioning ball 5-1 pops out, and the push button switch 5-2 is released under the action of the positioning ball 5-1. The auxiliary cylinder is started, and the auxiliary cylinder supplies hydraulic oil into the hydraulic groove 6. The auxiliary cylinder fills the hydraulic groove 6 with hydraulic oil. Under the push of the hydraulic oil, the push plate 7 pushes one side of the clamping block 8 outward, but the locking block does not completely push out of the hydraulic groove 6, and the wedge-shaped part of the locking block is still in the hydraulic groove 6. The wedge-shaped part of the clamping block 8 can support the pressure generated by the die 4 pressing the blank holder 2 downward. Since the main cylinder continuously pushes the die 4 downward, at this time, the wedge-shaped part of the clamping block 8 will be pressed into the through groove of the blank holder 2 under the action of the strong pressure. When the clamping block 8 moves into the through groove of the blank holder 2, the clamping block 8 will push the U-shaped rod 10 to move outward. Since a torsion spring 11 is installed in the middle of the clamping block 8 and the other end of the U-shaped rod 10 is clamped in the limit groove 12 on the side of the die 4, the connection between the die 4 and the blank holder 2 is completed, so that the die 4 can move downward simultaneously with the blank holder 2, and it is not necessary for the push rod 5 to move downward synchronously with the die 4.

[0048] Specific implementation method of Embodiment 2:

[0049] The push rod 5 rises upward to push the blank holder 2. When the positioning bead 5-1 on the push rod 5 abuts against the blank holder 2, the push button switch 5-2 is squeezed, and the push button switch 5-2 controls the auxiliary cylinder to extract part of the hydraulic oil in the hydraulic groove 6. Under the action of the hydraulic oil, the push plate 7 moves towards the middle of the punch 3; when the top surface of the blank holder 2 is on the same plane as the top surface of the punch 3, the push rod 5 moves downward to return to the initial position, and the push button switch 5-2 controls the auxiliary cylinder to fill the hydraulic groove 6 with hydraulic oil. Under the action of the hydraulic oil, the push plate 7 moves towards the outside of the punch 3; the clamping block 8 is clamped into the hydraulic groove 6 provided on the punch 3 under the action of the spring 9. At this time, the blank holder 2 and the punch 3 are connected as a whole; the sheet material is placed on the top surface of the punch 3, and the main cylinder drives the die 4 to extrude the sheet material to form an annular protrusion; the auxiliary cylinder starts, and under the action of the hydraulic oil, the push plate 7 moves towards the clamping block 8 side, pushing out part of the clamping block 8 from the hydraulic groove 6. Since part of the clamping block 8 is still stuck in the hydraulic groove 6, the blank holder 2 and the punch 3 will not be separated; the main cylinder pushes the die 4 to continuously extrude downward, and the wedge-shaped part of the clamping block 8 is squeezed into the blank holder 2 under the action of the pressure; then the clamping block 8 pushes the U-shaped rod 10, and under the action of the torsion spring 11, the other end of the U-shaped rod 10 is in the limit groove 12 of the die 4, completing the connection between the blank holder 2 and the die 4, so that the die 4 and the blank holder 2 can move downward synchronously to realize the stretching of the sheet material.

[0050] The above are only embodiments of the present invention. Common knowledge such as specific structures and characteristics known in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicability of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to interpret the content of the claims.

Claims

1. A hot stretching forming device applicable to forming a spherical surface on a flat plate, comprising a blank holder for fixing the plate and preventing the plate from wrinkling during the stretching process, and a female die and a male die for the stretching process, characterized in that: The blank holder is a slidable circular ring that can move up and down. There are raised drawing beads on the top surface of the blank holder. The inner side of the drawing beads on the top surface of the blank holder is a flat surface. The bottom surface of the female die is provided with an annular groove that can cooperate with the drawing beads. The bottom end of the male die is connected with a disc-shaped bottom plate by screws. Through holes are vertically opened on the outer periphery of the bottom plate, and the through holes are evenly distributed on the outer periphery of the bottom plate. Push rods for pushing the blank holder to move are inserted into the through holes. There is a "T-shaped" hydraulic groove inside the bottom plate and the male die, and hydraulic oil is filled in the hydraulic groove. The bottom end of the hydraulic groove is connected to an auxiliary cylinder. Two sliding components are respectively slidably connected to both sides at the top end inside the hydraulic groove, and the sliding components are slidably and sealedly connected to the hydraulic groove. The sliding components are composed of two oppositely arranged push plates, and the two oppositely arranged push plates are fixedly connected by a rod. Positioning beads that can be telescoped are installed at the tops of the push rods on the left and right sides of the bottom plate. A pressing switch for controlling the start of the auxiliary cylinder is installed at the bottom end of the positioning beads. Through grooves are respectively horizontally opened on the left and right sides inside the blank holder. Clamping blocks that can slide horizontally are placed in the through grooves. One side of the clamping block facing the male die is wedge-shaped. A spring is connected to the side of the clamping block away from the male die. One end of the spring is fixed to the clamping block, and the other end is fixed to the inner side wall of the through groove opened on the blank holder. When stretching the sheet material, first raise the blank holder so that the top surface of the blank holder is on the same plane as the top surface of the male die. The clamping block extends into the hydraulic groove outside the push plate under the action of the spring. Under the action of the clamping block, the blank holder is connected to the male die, and the female die extrudes the sheet material. Under the action of the drawing beads, an annular protrusion for fixing the sheet material is pressed out. U-shaped rods are installed on the left and right sides of the blank holder. The middle of the U-shaped rod is rotatably connected to a cross bar protruding from the side wall of the blank holder. A torsion spring is arranged in the middle of the U-shaped rod. One end of the U-shaped rod is inserted into the through groove on the side of the blank holder and contacts the side of the clamping block away from the male die. At the same time, the other end of the U-shaped rod can be inserted into the limit groove arranged on the side of the female die, and the limit grooves are respectively opened on the bottom side of the female die.

2. The hot stretching forming device applicable to forming a spherical surface on a flat plate according to claim 1, wherein: Threaded holes are opened on the outer peripheral sides of the bottom plate, the blank holder and the female die, and lifting eye bolts are connected in the threaded holes.

3. The hot stretching forming device applicable to forming a spherical surface on a flat plate according to claim 1, characterized in that: A main cylinder for pushing the female die to move up and down is arranged above the female die. A through hole for exhausting air is vertically opened at the center of the top end surface of the female die.

4. A hot stretch forming device applicable to forming a spherical surface on a flat plate according to claim 1, characterized in that: A hoisting hole is opened at the center of the male die.

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