CN113102532B - Labor-saving forming method suitable for large-size thin-wall conical shell - Google Patents

Abstract

The invention discloses a labor-saving forming method suitable for large-sized thin-walled conical shells. First, a mold is assembled and corrected, then a blank is put into a "U"-shaped inner cavity, heated to a forming temperature and kept warm, and then a sizing belt is attached. The cylindrical punch extrudes the middle of the billet, and the two sides of the billet gradually flow from the lower part to the upper part to produce a reverse extrusion movement. When the cylindrical punch is lowered to a predetermined depth, the bottom and wall of the billet have wall thickness. At this time, the preformed billet The cross section is "U" shaped, unloading, and then the cylindrical punch is replaced with a conical punch, the "U" shaped die is replaced with a conical die, corrected, and then the "U" shaped blank is put into the cone In the middle of the inner cavity, the conical punch moves downward, the upper part of the blank is flaring and deformed, and the lower part of the blank is constricted and deep drawn. When the conical punch drops to a predetermined depth, the final formed blank section Conical shape, and finally unloading. This case effectively reduces the forming load, reduces friction, and makes the forming of the conical shell more labor-saving and convenient.

Description

Labor-saving forming method suitable for large-size thin-wall conical shell

Technical Field

The invention relates to the technical field of metal plastic processing technology and forming, in particular to a labor-saving forming method suitable for a large-size thin-wall conical shell.

Background

In the traditional plastic forming process, the forming method of the thin-wall conical piece mainly comprises deep drawing forming, extrusion forming and spinning forming. The deep drawing forming is generally used for thin-wall parts, and the method has the advantages of simple operation and high material utilization rate, and has the defects of high requirements on the strength and the plasticity of the material, easy instability generation and difficult control of the wall thickness of the part; the extrusion forming mainly adopts a backward extrusion process, metal is in a strong three-dimensional compressive stress state during extrusion, the plasticity of the metal can be fully exerted, and a large deformation is obtained, and the defects that the requirement on equipment load is high and the wall thickness difference is easy to generate are overcome; the spinning forming is also a processing method of thin-wall parts, and has the advantages of short die development period, low cost, small spinning pressure, capability of completing the processes of forming, trimming and the like in one-time clamping, difficulty in realizing mass production and overhigh equipment cost.

In the extrusion forming process of the large-size thin-wall conical part, the common processing technology is to extrude the blank by using a proper male die and a proper female die to complete the one-step forming of the large-size thin-wall conical shell. The technology realizes the forming of the blank by using a backward extrusion method, can reduce forming procedures and realize one-time extrusion forming. The extrusion forming process is shown in figure 1: and (3) putting the blank into a female die, heating to a certain temperature, preserving heat for a period of time, then extruding the blank by using a male die, moving out the male die after the extrusion is finished, and then taking out the shell to finish the forming process of the conical shell. Although this method appears simple, there are still a number of disadvantages with this method:

(1) the requirement on extrusion equipment is high, and the tonnage is large. In the forming process, because the blank is always in contact with the die, a large friction force is generated in the extrusion process, the severe friction condition can block the flow of metal, the forming load is obviously increased, and the energy consumption and the cost are increased.

(2) The die is easily worn and damaged. The blank and the die generate great friction force and great heat in the forming process, the die is seriously abraded, and the male die is easy to break in the extrusion process due to the large height-diameter ratio of the male die.

(3) The dimensional accuracy of the part is poor. For the formation of the conical member, the dimensional accuracy of the part formed at one time is poor, and it is difficult to realize the formation of a precision instrument or a part.

(4) The mold is difficult to demold. When an extrusion part with a complex surface shape is formed, the extrusion part is closely contacted with a die due to large load and thin thickness of the extrusion part during extrusion, the extrusion part is easily adhered with the die, and the die is difficult to demould.

Disclosure of Invention

The invention aims to provide a labor-saving forming method suitable for a large-size thin-wall conical shell, overcomes the defects of the prior art, effectively reduces forming load, reduces friction, and enables the conical shell to be formed more conveniently and more labor-saving.

In order to achieve the above purpose, the solution of the invention is:

a labor-saving forming method suitable for a large-size thin-wall conical shell comprises the following steps:

s1: correcting the die: the complete die suitable for labor-saving forming of the large-size thin-wall conical shell comprises an upper die plate component arranged on an upper workbench of a press machine, two male dies capable of being replaced on the upper die plate component, a lower die plate component arranged on a lower workbench of the press machine, two female dies capable of being replaced on the lower die plate component and an ejector rod connected with an ejection cylinder of the press machine, wherein the two male dies comprise a cylindrical male die with a bearing and a replaceable conical male die, the two female dies comprise a U-shaped female die used in a complete set with the cylindrical male die with the bearing and a conical female die used in a complete set with the conical male die, the lower part of the cylindrical male die with the bearing is provided with a bearing with the diameter larger than that of the upper part, and the rest diameters of the cylindrical male die with the bearing and the bearing are the same except for the bearing part, the diameter of the upper part of the conical inner cavity is larger than that of the upper part of the cylindrical male die with the bearing and the diameter of the lower part of the conical inner cavity is smaller than that of the lower part of the cylindrical male die with the bearing and the bearing, the U-shaped female die is provided with a U-shaped inner cavity for the cylindrical male die to be placed in, a pre-forming gap is reserved between the U-shaped inner cavity and the cylindrical male die with the bearing and the bearing, the conical female die is provided with a conical inner cavity, the diameter of the upper part of the conical inner cavity is larger than that of the U-shaped inner cavity, the diameter of the lower part of the conical inner cavity is smaller than that of the U-shaped inner cavity, the conical inner cavity is used for the conical male die to be placed in, a final-forming gap is reserved between the conical inner cavity and the conical male die, and a lower die plate component corresponding to the lower part of the U-shaped inner cavity and the lower part of the conical inner cavity is provided with an ejection hole for placing an ejector rod, the die is characterized in that a bearing sizing belt cylindrical male die and a U-shaped female die are assembled firstly, and the position of the bearing sizing belt cylindrical male die is adjusted to enable the bearing sizing belt cylindrical male die and the U-shaped female die to be located on the same axis;

s2: discharging: after correcting the die, putting the columnar blank into a U-shaped inner cavity, heating to a forming temperature and preserving heat;

s3: performing extrusion: the sizing band cylindrical male die gradually extrudes the middle part of the blank along with the downward movement of the sizing band cylindrical male die, and because a preformed gap is reserved between the sizing band cylindrical male die and the U-shaped inner cavity, two sides of the blank gradually flow from the lower part to the upper part to generate backward extrusion movement;

s4: unloading the U-shaped blank: after the preforming process is finished, lifting the cylindrical male die with the bearing belt, and ejecting the blank by using an ejector rod;

s5: replacing and correcting the die: replacing the cylindrical male die with the bearing sizing band with a conical male die and replacing the U-shaped female die with a conical female die, namely completing the replacement of the die, correcting the conical male die and the conical female die and ensuring that the conical male die and the conical female die are positioned on the same axis;

s6: discharging: putting the preformed and extruded U-shaped blank into a conical female die, and ensuring that the U-shaped blank is placed in the middle of a conical inner cavity;

s7: final forming and extruding: the conical male die gradually moves downwards under the control of a workbench on a press, the conical male die extends into the U-shaped blank and drives the blank to move downwards, a final forming gap is reserved between the conical male die and the conical inner cavity, so that the two edges of the blank flow along the final forming gap to generate stretching movement, the conical male die contacts the upper part of the U-shaped blank to generate flaring deformation, at the moment, stretching instability can occur, the lower part of the U-shaped blank contracts and stretches when the conical male die moves to the lower part of the U-shaped blank, the original straight U-shaped blank is drawn in a conical shape, the stretching instability gradually disappears along with the operation of the conical male die, the bottom of the blank has the wall thickness when the conical male die descends to a preset depth, at the moment, the section of the finally-formed blank is in a conical shape, and the final forming extrusion of the blank is completed;

s8: discharging by using a conical shell: and after the final forming process is finished, lifting the conical male die, ejecting the conical shell out of the conical female die by using the ejector rod, and then taking out the formed conical shell to finish the unloading process.

After the scheme is adopted, the gain effect of the invention is as follows:

(1) compared with the traditional one-time extrusion forming process, the labor-saving forming process can greatly reduce the load and the friction force of the forming process, obviously reduce the energy consumption and avoid the strict requirement of the forming of a large-size thin-wall conical shell on the tonnage of equipment;

(2) because of the load reduction and labor saving advantages, the service life of the die is greatly prolonged;

(3) due to the load reduction and labor saving advantages, the deformation of the male die caused by unbalance loading is avoided, namely the dimensional accuracy of the male die in the forming process is ensured, the dimensional accuracy of the conical part determined by the dimensional accuracy of the male die is further ensured, and the product percent of pass is improved;

(4) because of small tonnage of equipment, long service life of the die and high qualification rate of products, the production cost is reduced.

Drawings

FIG. 1 is a schematic extrusion view of a conventional die;

FIG. 2 is a schematic structural diagram of a die for mounting a cylindrical male die and a U-shaped female die of a bearing belt according to an embodiment of the invention;

FIG. 3 is a schematic view of the working state of a pre-extrusion pre-deformation discharge mold according to an embodiment of the present invention;

FIG. 4 is a schematic view of the working condition of the die during pre-extrusion deformation according to an embodiment of the present invention;

FIG. 5 is a schematic view of the die operating state at the end of pre-extrusion according to one embodiment of the present invention;

FIG. 6 is a schematic view of the working state of the discharging die after the pre-extrusion is finished according to one embodiment of the present invention;

FIG. 7 is a schematic structural diagram of a mold for replacing a tapered male mold and a tapered female mold according to an embodiment of the present invention;

FIG. 8 is a schematic view of the working state of the die for discharging before final extrusion deformation according to an embodiment of the present invention;

FIG. 9 is a schematic view of the die operating conditions during final extrusion deformation in accordance with one embodiment of the present invention;

FIG. 10 is a schematic view of the die operating conditions after final extrusion deformation is complete in accordance with one embodiment of the present invention;

FIG. 11 is a schematic view of the die operating conditions at the end of extrusion according to one embodiment of the present invention;

FIG. 12 is a schematic view of the working state of the discharging die after the end of the final extrusion according to one embodiment of the present invention;

FIG. 13 is a schematic view of an "U" shaped blank extrusion into a tapered shell in accordance with an embodiment of the present invention;

FIG. 14 is a top view of a mold in accordance with one embodiment of the invention.

Reference numerals:

the die comprises an upper die plate component 1, an upper die plate 11, a punch backing plate 12, an upper die pin 13, an upper die screw 14, a cylindrical punch 2 with a bearing and a bearing, a combined head 21, a screw head 22, a bearing 23, a conical punch 3, a lower die plate component 4, a lower die plate 41, a die backing plate 42, a lower die pin 43, a lower die screw 44, an ejection hole 45, a U-shaped female die 5, a U-shaped inner cavity 51, a pre-forming gap 52, an arc surface 53, a conical female die 6, a conical inner cavity 61, a final-forming gap 62, an ejector rod 7, a rod body 71, an ejector block 72, a material baffle plate 8, a positioning block 9, a pre-stressing ring 10 and a blank 100.

Detailed Description

The invention is described in detail below with reference to the accompanying drawings and specific embodiments.

As shown in figure 2, the invention relates to a complete die suitable for labor-saving forming of a large-size thin-wall conical shell, which comprises an upper die plate component 1 arranged on an upper workbench (not shown in the figure) of a press, two male dies capable of being replaced on the upper die plate component 1, a lower die plate component 4 arranged on a lower workbench (not shown in the figure) of the press, two female dies capable of being replaced on the lower die plate component 4 and a mandril 7 connected with an ejecting cylinder (not shown in the figure) of the press.

With reference to fig. 2 and 7, the two punches comprise a bearing cylindrical punch 2 and a replaceable conical punch 3, the two dies comprise a "U" shaped die 5 for use in set with the bearing cylindrical punch 2 and a conical die 6 for use in set with the conical punch 3,

the concrete mounting structure of the male die on the upper die plate assembly 1 is, as shown in fig. 2, the upper die plate assembly 1 comprises an upper die plate 11, a male die backing plate 12, an upper die pin 13 and an upper die screw 14, an upper pin hole and an upper screw hole are formed in the upper end surface of the male die, a left through hole is formed in the position, corresponding to the upper pin hole, of the upper die plate 11 and the male die backing plate 12, the upper pin 13 penetrates through the left through hole and then is placed into the upper pin hole to achieve positioning, similarly, a right through hole is also formed in the position, corresponding to the upper screw hole, of the upper die plate 11 and the male die backing plate 12, and the upper die screw 14 penetrates through the right through hole and then is matched with the upper screw hole to achieve fixing, so that the male die is connected with the male die backing plate 12 and the upper die plate 11.

The concrete mounting structure of die on lower bolster subassembly 4 does, as figure 2, lower bolster subassembly 4 includes lower bolster 41, die backing plate 42, lower mould pin 43 and lower mould screw 44, pinhole and lower screw down are seted up to the lower terminal surface of die, the right perforation is seted up in the position that corresponds pinhole down to lower bolster 41 and die backing plate 42, and lower mould pin 43 passes and puts into down the pinhole behind the right perforation and realize the location, and in the same way, left perforation is also seted up in the position that corresponds screw down to lower bolster 41 and die backing plate 42, and lower mould screw 44 passes and realizes fixedly with the screw cooperation down after left perforation, thereby the die links together with die backing plate 42, lower bolster 41.

As shown in fig. 2, the U-shaped female die 5 is provided with a U-shaped inner cavity 51, the U-shaped inner cavity 51 is used for placing the bearing cylindrical male die 2, a pre-forming gap 52 is reserved between the U-shaped inner cavity 51 and the bearing cylindrical male die 2, as shown in fig. 7, the conical female die 6 is provided with a conical inner cavity 61, the upper diameter of the conical inner cavity 61 is larger than that of the U-shaped inner cavity 51, the lower diameter of the conical inner cavity 61 is smaller than that of the U-shaped inner cavity 51, the conical inner cavity 61 is used for placing the conical male die 3, a final-forming gap 62 is reserved between the conical inner cavity 61 and the conical male die 3, and the lower die plate assembly 4 corresponding to the lower position of the U-shaped inner cavity 51 and the lower position of the conical inner cavity 61 is provided with a communicated ejection hole 45 for placing the ejector rod 7. In a preferred embodiment, the ejector rod 7 comprises a rod body 71 and an ejector block 72 detachably connected to the top of the rod body 71, the rod body 71 and the ejector block 72 are detachably connected through a screw, the ejector block 72 is connected with the ejector rod 7 with a screw head 22 through a screw thread, and the ejector block 72 is located inside the die base plate 42. The punch backing plate 12 and the die backing plate 42 serve to prevent the upper die plate 11 and the lower die plate 41 from being damaged by the pressing impact.

Meanwhile, the central lines of the female die and the male die are kept on the same straight line, so that the uneven stress of the workpiece is avoided.

As shown in FIG. 13, the bearing diameter of the bearing cylindrical punch 2 is 10-20 mm larger than the diameter of the upper part, the diameters of the bearing cylindrical punch 2 except the bearing diameter are the same, the diameter of the upper part of the conical inner cavity 61 is larger than the diameter of the upper part of the bearing cylindrical punch 2, the diameter of the lower part of the conical inner cavity 61 is smaller than the diameter of the lower part of the bearing cylindrical punch 2,

in the scheme, the cylindrical punch 2 with the bearing and the bearing is formed by connecting an upper part and a lower part which are detachably connected, namely, the lower end of the cylindrical punch 2 with the bearing and the bearing is detachably connected with a combination head 21, the edge of the lower end of the combination head 21 protrudes outwards to form a bearing 23, the detachable connection is a screw joint, and the lower end of the cylindrical punch 2 with the bearing and the bearing is connected with the combination head 21 with a screw head 22 through a thread. The detachable design mainly considers that the bearing belt 23 can be conveniently replaced under the condition that the cylindrical punch 2 of the bearing belt is worn and broken.

The lower end of the inner wall of the U-shaped inner cavity 51 forms an inward-folded cambered surface 53. Because the right-angled portion tends to result in underfilling of the billet 100, at locations where the billet 100 metal flow is slow, particularly at the corners, an inside camber surface 53 corresponding to a transition fillet is designed to make the billet 100 metal flow smoother and the filling more complete.

In a preferred embodiment, the mold further comprises a prestressed ring 10, the prestressed ring 10 is a hollow annular ring, and the prestressed ring 10 is sleeved in the U-shaped inner cavity 51 and attached to the inner wall of the U-shaped inner cavity 51. The prestressed ring 10 can prevent the U-shaped concave die 5 from being damaged. The absence of the pre-stressed ring 10 in the conical inner cavity 61 in fig. 8 is mainly due to the fact that the load required by the flaring and stretching process is small, the impact and the abrasion on the female die are small, and the additional pre-stressed ring 10 is not needed.

As shown in fig. 14, the upper end surface of the female die is provided with a rotatable striker plate 8 and a positioning block 9 around the opening of the inner cavity. In an embodiment, the number of the material blocking blocks and the number of the positioning blocks 9 are three, and three material blocking plates 8 and three positioning blocks 9 are respectively and uniformly arranged on the upper end surface of the female die around the cavity opening of the inner cavity. If the prestressed ring 10 is provided, the positioning block 9 is arranged on the upper end face of the prestressed ring 10.

The positioning block 9 is used for limiting the descending position of the female die and correcting the position of the male die so that the male die and the female die are integrally positioned on the same axis. The positioning block 9 is added in the discharging process to assist the striker plate 8 to clamp the formed blank 100, so that discharging is facilitated.

The striker plate 8 rotates the striker plate 8 by 90 degrees when unloading, so that the blank 100 is prevented from overflowing the female die during extrusion, and the striker plate 8 can also play a role in separating the male die from the blank 100 during demoulding, thereby being beneficial to demoulding.

The invention provides a labor-saving forming method suitable for a large-size thin-wall conical shell, which comprises the following specific steps of:

s1: correcting the die: firstly, fixing a U-shaped female die 5, a female die backing plate 42 and a lower die plate 41 together through a lower die pin 43 and a lower die screw 44, placing a prestress ring 10 in a U-shaped inner cavity 51, then installing a material baffle plate 8 and a positioning block 9, then connecting the lower end of a sizing band 23 in a sizing band cylindrical male die 2 with the upper end provided with a threaded hole through a screw head 22, then fixing the sizing band cylindrical male die 5, a male die backing plate 12 and an upper die plate 11 together through an upper die pin 13 and an upper die screw 14, and finally adjusting the position of the sizing band cylindrical male die 2 through the positioning block 9 to enable the sizing band cylindrical male die 2 and the U-shaped female die 5 to be positioned on the same axis;

s2: discharging: after the mould is corrected, the positioning block 9 is rotated, and then the columnar blank 100 is placed into the U-shaped inner cavity 51 and heated to the forming temperature and is insulated;

s3: performing extrusion: as shown in fig. 3 and 4, the striker plate 8 is rotated so that the long side of the striker plate 8 is located above the inner cavity of the pre-stressed ring 10, after the extrusion process starts, the calibrating tape cylindrical punch 2 gradually extrudes the middle part of the blank 100 along with the downward movement of the calibrating tape cylindrical punch 2, and because a pre-forming gap 52 is left between the calibrating tape cylindrical punch 2 and the U-shaped inner cavity 51, two sides of the blank 100 gradually flow from the lower part to the upper part to generate a backward extrusion movement, the wall thickness of the bottom of the blank 100 is ensured when the calibrating tape cylindrical punch 2 descends to a predetermined depth, at this time, the cross section of the pre-formed blank 100 is in a U shape (also called a cylindrical shape and a straight cylinder), and the pre-forming extrusion of the blank 100 is completed;

s4: unloading the U-shaped blank: as shown in fig. 5 and 6, after the preforming process is finished, the sizing cylindrical male die 2 is lifted, the blank 100 and the sizing cylindrical male die 2 are separated under the action of the striker plate 8, the sizing cylindrical male die 2 is removed after the sizing cylindrical male die 2 is separated from the blank 100, and then the blank 100 is ejected by the ejector rod 7;

s5: replacing and correcting the die: as shown in fig. 7, the cylindrical male die 2 with the bearing and the bearing belt is replaced by a conical male die 3, the U-shaped female die 5 is replaced by a conical female die 6, and the pre-stressed ring 10 is removed, so that the replacement of the die is completed, the striker plate 8 is installed and is in a non-striker state, and then the conical male die 3 and the conical female die 6 are corrected by the positioning block 9, so that the conical male die 3 and the conical female die 6 are ensured to be positioned on the same axis;

s6: discharging: as shown in fig. 8, the preformed and extruded U-shaped blank 100 is placed into the tapered female die 6, and the bottom arc of the U-shaped blank 100 is the same as the arc of the female die to automatically coincide with the arc of the female die due to the inward-folded arc 53 formed at the lower end of the inner wall of the U-shaped inner cavity 51, so that the U-shaped blank 100 can be stably placed in the middle of the tapered inner cavity 61;

s7: final forming and extruding: as shown in fig. 9 and 10, the position of the conical male die 3 is adjusted by the positioning block 9 so that the conical male die 3 and the conical female die 6 are located on the same axis, the striker plate 8 is rotated so that the long edge of the striker plate 8 is located above the orifice of the conical inner cavity 61, the striker plate 8 is in a striker state, the conical male die 3 gradually moves downwards under the control of the upper workbench of the press, the conical male die extends into the U-shaped blank and drives the blank to move downwards, because the final forming gap 62 is left between the conical male die 3 and the conical inner cavity 61, two edges of the blank 100 flow along the final forming gap 62 to generate a stretching motion, when the conical male die 3 starts to contact the U-shaped blank 100, flaring deformation of the upper part of the U-shaped blank 100 occurs, at this time, stretching instability can occur, when the conical male die 3 runs to the lower part of the U-shaped blank 100, the necking deep drawing of the lower part of the U-shaped blank 100 begins to occur, drawing the original flat U-shaped blank 100 into a cone, gradually losing tension instability along with the operation of the conical male die 3, and enabling the bottom of the blank 100 to have a wall thickness (namely the wall thickness of a conical shell) when the conical male die 3 descends to a preset depth, wherein the section of the finally formed blank 100 is conical, and the final forming and extrusion of the blank 100 are finished;

in other words, the billet 100 is first extruded into a cylindrical shell (diameter D) of equal wall thickness during the preforming process, and then the cylindrical shell is simultaneously flared and necked with the conical punch 3 during the final forming process, or flared first and then stretch-necked as the punch moves down to the lower portion of the cylindrical shell until the forming process is finished. As shown in fig. 13, the flare deformation is performed at a diameter equal to or larger than the boundary diameter (H portion), and the stretch necking is performed at a diameter equal to or smaller than the boundary diameter (H portion). The stretching and necking are performed with equal wall thickness, which is equivalent to the drawing and tapering of the original straight bottom surface of the cylindrical shell, so the friction force is small in the process, and the required load is small;

s8: discharging by using a conical shell: as shown in fig. 11 and 12, after the final forming process is finished, the conical male die 3 is lifted, the conical male die 3 is separated from the conical shell under the action of the striker plate 8, then the conical male die 3 is removed, then the striker plate 8 is retracted, the conical shell is ejected out of the conical female die 6 by the ejector rod 7, the conical shell is fixed by the positioning block 9 to prevent the conical shell from falling into the conical female die 6 when the ejector rod 7 falls down, and then the formed conical shell is taken out to complete the unloading process.

The final forming process assembly is shown in fig. 8: the assembly and connection is similar to that of pre-forming, with the difference that the final forming process can be cost-effective and can reduce energy consumption because the conical male die 3 can be made hollow without too much load.

The invention aims to overcome the defects and shortcomings of the existing large-size thin-wall conical shell in the forming process, combines extrusion forming and deep drawing-flaring technology, effectively reduces the equipment load in the forming process, and provides a labor-saving forming method with reasonable design, thereby realizing the labor-saving forming of the large-size thin-wall conical shell. The method is characterized in that the original one-time extrusion process is divided into two steps, namely, a pre-forming step and a final forming step. In the pre-forming process, the blank is firstly extruded into a cylindrical shell with equal wall thickness, then in the final forming process, the cylindrical shell is flared and necked by a conical male die at the same time, or the cylindrical shell is flared firstly and then stretched and necked along with the conical male die moving downwards to the bottom of the cylindrical part until the forming process is finished. As shown in fig. 2, the flare deformation is performed at a boundary diameter or more, and the stretch necking is performed at a boundary diameter or less. The stretching and necking are performed with equal wall thickness, which is equivalent to the drawing and tapering of the original straight bottom surface of the cylindrical shell, so the friction force in the process is small, and the required load is also small.

The technical core of the invention is that labor-saving forming can be realized for forming the large-size conical shell. The device consists of a backward extrusion preforming cylindrical part and a flaring-necking composite final forming conical part. Compared with the way of realizing labor-saving forming by one-time backward extrusion conical piece forming: in the procedure of reversely extruding the preformed cylindrical part: the backward extrusion conical part is formed at one time, the die is in full contact with the wall of the conical part, and the friction force is large; only the punch bearing belt 23 area of the preformed cylindrical part is in contact with the wall part of the cylindrical part in a backward extrusion way, so that the contact area and the corresponding friction force are greatly reduced, and the forming load is reduced; secondly, in the working procedure of backward extruding the preformed cylindrical part: the backward extrusion conical piece is formed in one step, and the stress projection area of the blank is the large end area of the conical piece; the pre-forming straight cylinder is subjected to backward extrusion, the stressed projection area of the blank is the cross section area of the straight cylinder, and the area is about the cross section area at the height of the conical piece 1/2 and is smaller than the large end area of the conical piece, so that the forming load is reduced; in the flaring-necking composite final forming conical part, the back extrusion conical part is formed once, and the blank is in a three-dimensional pressure state; in the process of flaring-necking composite final forming conical parts, a blank is in a two-pulling-one-compression stress state when flaring and necking are carried out, so that the forming load is reduced.

And in the preforming stage, the blank is extruded into a cylindrical shell by adopting a backward extrusion technology, and the cylindrical shell has the characteristic of equal wall thickness. During preforming, the lower end of the male die is provided with the sizing belt 23, the blank is almost not contacted with the male die after passing through the sizing belt 23 in the backward extrusion process, and the friction force and the frictional heat generation in the forming process can be greatly reduced, so that the forming load is reduced. The thickness of the inner curved surface 53 of the cylindrical part is consistent with the wall thickness, and the radian of the bottom edge of the cylindrical part is consistent with the radian of the inner wall of the final forming female die, so that the cylindrical part can be kept stable even if suspended. And then placing the preformed cylindrical part into a final forming female die, and carrying out flaring-deep drawing composite forming on the cylindrical part to finally obtain the required thin-wall shell. The drawing and necking process is an equal wall thickness drawing process, the forming process of the conical shell is equivalent to the process of expanding a flat bottom surface into a cone, and the wall thickness is not thinned in the process. The friction force in the process is small, and the required load is also small.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the design of the present invention, and all equivalent changes made in the design key point of the present invention fall within the protection scope of the present invention.

Claims (1)

1. A labor-saving forming method suitable for a large-size thin-wall conical shell is characterized by comprising the following steps of: the method comprises the following steps:

s1: correcting the die: the complete die suitable for labor-saving forming of the large-size thin-wall conical shell comprises an upper die plate component arranged on an upper workbench of a press machine, two male dies capable of being replaced on the upper die plate component, a lower die plate component arranged on a lower workbench of the press machine, two female dies capable of being replaced on the lower die plate component and an ejector rod connected with an ejection cylinder of the press machine, wherein the two male dies comprise a cylindrical male die with a bearing and a replaceable conical male die, the two female dies comprise a U-shaped female die used in a complete set with the cylindrical male die with the bearing and a conical female die used in a complete set with the conical male die, the lower part of the cylindrical male die with the bearing is provided with a bearing with the diameter larger than that of the upper part, and the rest diameters of the cylindrical male die with the bearing and the bearing are the same except for the bearing part, the diameter of the upper part of the conical inner cavity is larger than that of the upper part of the cylindrical male die with the bearing and the diameter of the lower part of the conical inner cavity is smaller than that of the lower part of the cylindrical male die with the bearing and the bearing, the U-shaped female die is provided with the U-shaped inner cavity for the cylindrical male die to be placed in, a pre-forming gap is reserved between the U-shaped inner cavity and the cylindrical male die with the bearing and the bearing, the conical female die is provided with the conical inner cavity, the diameter of the upper part of the conical inner cavity is larger than that of the U-shaped inner cavity, the diameter of the lower part of the conical inner cavity is smaller than that of the U-shaped inner cavity, the conical inner cavity is used for the conical male die to be placed in, a final forming gap is reserved between the conical inner cavity and the conical male die, and an ejection hole communicated with the lower die plate component corresponding to the lower part of the U-shaped inner cavity and the lower part of the conical inner cavity is formed for the ejector rod to be placed, the die is characterized in that a bearing sizing belt cylindrical male die and a U-shaped female die are assembled firstly, and the position of the bearing sizing belt cylindrical male die is adjusted to enable the bearing sizing belt cylindrical male die and the U-shaped female die to be located on the same axis;

s2: discharging: after correcting the die, putting the columnar blank into a U-shaped inner cavity, heating to a forming temperature and preserving heat;

s3: performing extrusion: the sizing band cylindrical male die gradually extrudes the middle part of the blank along with the downward movement of the sizing band cylindrical male die, and because a preformed gap is reserved between the sizing band cylindrical male die and the U-shaped inner cavity, two sides of the blank gradually flow from the lower part to the upper part to generate backward extrusion movement;

s4: unloading the U-shaped blank: after the preforming process is finished, lifting the cylindrical male die with the bearing belt, and ejecting the blank by using an ejector rod;

s5: replacing and correcting the die: replacing the cylindrical male die with the bearing sizing band with a conical male die and replacing the U-shaped female die with a conical female die, namely completing the replacement of the die, correcting the conical male die and the conical female die and ensuring that the conical male die and the conical female die are positioned on the same axis;

s6: discharging: putting the preformed and extruded U-shaped blank into a conical female die, and ensuring that the U-shaped blank is placed in the middle of a conical inner cavity;

s7: final forming and extruding: the conical male die gradually moves downwards under the control of a workbench on a press, the conical male die extends into the U-shaped blank and drives the blank to move downwards, a final forming gap is reserved between the conical male die and the conical inner cavity, so that the two edges of the blank flow along the final forming gap to generate stretching movement, the conical male die contacts the upper part of the U-shaped blank to generate flaring deformation, at the moment, stretching instability can occur, the lower part of the U-shaped blank is drawn and contracted when the conical male die runs to the lower part of the U-shaped blank, the original straight U-shaped blank is drawn in a conical shape, the stretching instability gradually disappears along with the running of the conical male die, the bottom of the blank has the wall thickness when the conical male die descends to a preset depth, at the moment, the section of the finally-formed blank is conical, and the final forming extrusion of the blank is completed;

s8: discharging by using a conical shell: and after the final forming process is finished, lifting the conical male die, ejecting the conical shell out of the conical female die by using the ejector rod, and then taking out the formed conical shell to finish the unloading process.

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