CN108856328B - Reverse extrusion die suitable for blank thick-wall pipe with poor plasticity and design method - Google Patents

Reverse extrusion die suitable for blank thick-wall pipe with poor plasticity and design method Download PDF

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CN108856328B
CN108856328B CN201710335621.9A CN201710335621A CN108856328B CN 108856328 B CN108856328 B CN 108856328B CN 201710335621 A CN201710335621 A CN 201710335621A CN 108856328 B CN108856328 B CN 108856328B
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die
diameter
blank
upper die
core
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CN108856328A (en
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卢云
吴志林
陈智仁
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Nanjing University of Science and Technology
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Nanjing University of Science and Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C25/00—Profiling tools for metal extruding
    • B21C25/02—Dies
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C23/00—Extruding metal; Impact extrusion
    • B21C23/02—Making uncoated products
    • B21C23/20—Making uncoated products by backward extrusion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C25/00—Profiling tools for metal extruding
    • B21C25/04—Mandrels

Abstract

The invention discloses a backward extrusion die suitable for a metal thick-wall pipe with poor plasticity, which comprises a positioning plate, an upper die, a die core and a lower die; the upper die positioning plate is of a cylindrical cavity structure, the die core is arranged in a central hole of the upper die positioning plate, and the upper die is arranged at the lower end of the upper die positioning plate; the upper die is of a cylindrical cavity structure, and the die core is of a cylindrical structure; the inner diameter of the upper die is larger than the outer diameter of the die core; the positioning plate combines the upper die and the die core to form a male die; the upper die, the die core and the lower die are coaxially arranged; when the male die and the lower die are assembled, a backward extrusion die of the blank is formed; the design method of the mold comprises the following steps: step 1, determining the outer diameter of the end head at the lower end of a mold core and the inner diameter of the end head at the lower end of an upper mold according to the size requirement of a thick-wall pipe to be formed; step 2, determining the diameter and height of the blank according to the equal volume principle of extrusion deformation; step 3, determining the outer diameter of the end head at the lower end of the upper die and the inner diameter of the lower die of the die according to the diameter and the height of the blank; the backward extrusion die has large tensile wall thickness and improves the qualification rate.

Description

Reverse extrusion die suitable for blank thick-wall pipe with poor plasticity and design method
Technical Field
The invention belongs to the field of blank processing, and particularly relates to a reverse extrusion die and a design method suitable for a blank thick-wall pipe with poor plasticity.
Background
For the backward extrusion forming of a blank pipe type part, the adopted mould is a structure mode of a mandrel male mould and a cylinder type part female mould. During backward extrusion deformation, only the pipe wall material part close to the mandrel generates larger stretching deformation, and through the stress-strain relationship in the material, the material deformation close to the mandrel part drives the material far away from the mandrel to generate deformation. For the blank materials with poor plasticity (such as AZ80, AZ31 magnesium alloy and the like), when a thicker thick-wall (the wall thickness is more than 20mm) pipe is formed by backward extrusion, the stress of the inner wall of the pipe cannot be timely transmitted to the outer wall of the pipe, so that the material of the outer wall cannot be timely supplied, and the outer wall of the pipe is provided with one circle of circumferential cracks.
The journal of the hot working process has a title of computer simulation research on the backward extrusion process of AZ31 magnesium alloy pipes based on DEFORM-3D software, and the article concludes that only a magnesium alloy cylinder with a pipe wall of 1mm can be backward extruded and formed at 300 ℃, so that only a magnesium alloy cylinder with a pipe wall of 1mm can be backward extruded under the heating condition.
Disclosure of Invention
The invention aims to provide a reverse extrusion die for a blank thick-wall pipe with poor plasticity and a design method thereof, so as to solve the problem that the blank thick-wall pipe with poor plasticity is difficult to form.
The technical solution for realizing the purpose of the invention is as follows:
a backward extrusion die suitable for metal thick-wall pipes with poor plasticity comprises a positioning plate, an upper die, a die core and a lower die; the upper die positioning plate is of a cylindrical cavity structure, the die core is installed in a central hole of the upper die positioning plate, and the upper die is installed at the lower end of the upper die positioning plate; the upper die is of a cylindrical cavity structure, and the die core is of a cylindrical structure; the inner diameter of the upper die is larger than the outer diameter of the die core; the positioning plate combines the upper die and the die core to form a male die; the upper die, the die core and the lower die are coaxially arranged; and when the male die and the lower die are assembled, a backward extrusion die of the blank is formed.
A design method suitable for a backward extrusion die of a metal thick-wall pipe with poor plasticity comprises the following steps:
step 1, determining the outer diameter of the end head at the lower end of a mold core and the inner diameter of the end head at the lower end of an upper mold according to the size requirement of a thick-wall pipe to be formed:
if the height of the pipe is h, the inner diameter is d1 and the outer diameter is d2, the intermediate diameter of the pipe is as follows:
Figure BDA0001293729500000021
according to the size of the pipe, the outer diameter of the end head (namely a circular boss) at the lower end of the mold core can be determined to be d1, and the inner diameter of the end head (annular boss) at the lower end of the upper mold is d 2;
step 2, determining the diameter and height of the blank according to the equal volume principle of extrusion deformation:
according to the equal volume principle of extrusion deformation, the following characteristics are obtained: vE＝VC、VB＝VF；
VEThe volume of the part inside the middle diameter of the cylindrical blank; vBThe volume of the part outside the middle diameter of the cylindrical blank; vCThe volume of the part inside the middle diameter of the extruded pipe; vFThe volume of the part outside the middle diameter of the extruded pipe;
according to VE＝VC、VB＝VFThe following can be obtained:
Figure BDA0001293729500000022
wherein h' is the height of the blank and D is the diameter of the blank;
substituting ① into ② and ③ to obtain:
Figure BDA0001293729500000024
the dimensions of the optimized blank thus determine that the blank is a solid cylinder with a diameter D and a height h';
step 3, determining the outer diameter of the end head at the lower end of the upper die and the inner diameter of the lower die of the die according to the diameter and the height of the blank:
namely, the outer diameter of the end head at the lower end of the upper die of the die is D, and the inner diameter of the lower die is D.
Compared with the prior art, the invention has the following remarkable advantages:
(1) the backward extrusion die does not need heating, has large tensile wall thickness, and improves the qualification rate:
the backward extrusion die comprehensively utilizes the action among the die core, the upper die and the lower die, so that the inner wall and the outer wall of the blank are simultaneously extruded, the wall thickness of the obtained pipe is large, and the product percent of pass is improved.
(2) The forming performance is good: according to the backward extrusion die, the die angle is arranged on the inner wall of the lower end of the upper die 3, so that the capability of upward plastic deformation of the outer wall of the extruded blank along the die angle is further improved, and the forming performance is good.
(3) Easy demoulding: according to the backward extrusion die, the circular boss is arranged at the lower end of the die core, and the annular boss is arranged on the inner wall of the lower end of the upper die, so that the die is easy to demould.
The present invention is described in further detail below with reference to the attached drawing figures.
Drawings
FIG. 1 is a schematic view of the structure of the billet counter-extrusion die before extrusion.
FIG. 2 is a schematic diagram of the position structure of the billet backward extrusion die during extrusion.
Fig. 3 is a schematic view of the upper mold structure.
Fig. 4 is a schematic view of a mold core structure.
Fig. 5 is a partially enlarged view of fig. 2.
FIG. 6 is a flow chart of a design method of a backward extrusion die for thick-wall metal pipes.
FIGS. 7(a) - (b) are comparative diagrams of AZ80 magnesium alloy tubes with 22mm wall thickness obtained by backward extrusion with a conventional backward extrusion die (front) and a backward extrusion die (rear) according to the present invention, respectively
Detailed Description
For the purpose of illustrating the technical solutions and technical objects of the present invention, the present invention will be further described with reference to the accompanying drawings and specific embodiments.
With reference to fig. 1-2, the backward extrusion die for thick-wall metal pipes with poor plasticity comprises a positioning plate 1, a blank holder 2, an upper die 3, a die core 4, a lower die 5 and a bottom plate 7; the upper die positioning plate 1 is of a cylindrical cavity structure, the die core 4 is arranged in a central hole of the upper die positioning plate 1, and the upper die 3 is arranged on an annular boss at the lower end of the upper die positioning plate 1; the lower ends of the upper die 3 and the die core 4 are flush, the upper die 3 is of a cylindrical cavity structure, and the die core 4 is of a cylindrical structure; the inner diameter of the upper die 3 is larger than the outer diameter of the die core 4, and a gap between the upper die and the die core is used as a metal blank 6 extrusion deformation space; the positioning plate 1 combines an upper die 3 and a die core 4 to form a male die; the lower die 5 is arranged on the bottom plate 7; the edge pressing plate 2 is arranged at the upper end of the lower die 5, and the edge pressing plate 2 presses the lower die 5 and the bottom plate 7 during demolding, so that the upper die 3 is separated from the lower die 5 from the upper side; the upper die 3, the die core 4 and the lower die 5 are coaxially arranged; the male die and the lower die 5 form a backward extrusion die of the blank 6 when the dies are closed.
Further, with reference to fig. 3, a die angle is arranged on the inner wall of the lower end of the upper die 3, the die angle is convenient for demoulding of the upper die 3, and the outer wall blank 6 is subjected to upward plastic deformation along the die angle after the blank is extruded.
Further, with reference to fig. 4, in order to facilitate demolding, a circular boss is arranged at the lower end of the mold core 4, the diameter of the circular boss is larger than that of the mold core 4, and the diameter difference is within 1 mm; meanwhile, the inner wall of the lower end of the upper die 3 is provided with an annular boss, and the difference between the inner diameter of the annular boss and the inner diameter of the upper die 3 is 1-3 mm; a cylindrical block 8 is arranged in the center of the bottom plate 7, and the cylindrical block 8 and the bottom plate 7 are of detachable structures; firstly, fixing the cylindrical block 8 and the bottom plate 7, extruding the mold core 4 downwards, removing the cylindrical block 8 after the blank 6 is formed, and continuously extruding the mold core 4 downwards to separate from the lower end of the bottom plate 7; the positioning plate 1 is separated from the upper end of the upper die 3, and the blank 6 is taken out from the upper die 3.
The positioning plate 1 is uniformly pressed by using a three-action hydraulic press, so that the upper die 3 and the die core 4 simultaneously extrude the blank 6, the outer edge and the central part of the cylindrical blank 6 with poor plasticity are simultaneously extruded, and meanwhile, stress is transferred to the central part of the wall thickness of the formed thick-wall pipe, so that the blank 6 flows upwards, and the pipe is formed between the upper die 3 and the die core 4. And after the pipe is extruded, the detachable cylindrical block 8 in the center of the bottom plate 7 is taken down, and acting force is continuously applied to the mold core 4 to enable the mold core to be separated from the lower end of the bottom plate 7. The edge pressing plate 2 and the positioning plate 1 are sequentially taken down from the upper end of the die, the formed pipe is taken out from the upper end of the upper die 3, and finally the upper die 3 and the lower die 5 are dismounted.
With reference to fig. 6, according to the backward extrusion mold for thick-walled metal pipes, the invention provides a design method suitable for the backward extrusion mold for thick-walled metal pipes with poor plasticity, which comprises the following steps:
step 1, determining the outer diameter of the end head at the lower end of a mold core 4 and the inner diameter of the end head at the lower end of an upper mold 3 according to the size requirement of a thick-wall pipe to be formed:
with reference to fig. 4 and 5, if the height of the tube is h, the inner diameter is d1, and the outer diameter is d2, the middle diameter of the tube is:
Figure BDA0001293729500000041
according to the size of the pipe, the outer diameter of the end head (namely the circular boss) at the lower end of the mold core 4 can be determined to be d1, and the inner diameter of the end head (the annular boss) at the lower end of the upper mold 3 can be determined to be d 2.
Step 2, determining the diameter and height of the blank according to the equal volume principle of extrusion deformation:
according to the equal volume principle of extrusion deformation, the following characteristics are obtained: vE＝VC、VB＝VF；
Wherein the intermediate diameter of the wall thickness of the pipe is used as a boundary line, VEThe volume of the part inside the middle diameter of the cylindrical blank; vBThe volume of the part outside the middle diameter of the cylindrical blank; vCThe volume of the part inside the middle diameter of the extruded pipe; vFThe volume of the part outside the middle diameter of the extruded pipe;
according to VE＝VC、VB＝VFThe following can be obtained:
Figure BDA0001293729500000042
wherein h' is the height of the blank and D is the diameter of the blank;
substituting ① into ② and ③ to obtain:
Figure BDA0001293729500000051
Figure BDA0001293729500000052
the dimensions of the optimized blank thus determine that the blank is a solid cylinder with a diameter D and a height h'.
Step 3, determining the outer diameter of the end head at the lower end of the upper die and the inner diameter of the lower die of the die according to the diameter and the height of the blank:
namely, the outer diameter of the end head at the lower end of the upper die 3 of the die is D, and the inner diameter of the lower die 5 is D.
Example 1
The AZ80 magnesium alloy pipe material with inner diameter d 1-91 mm, outer diameter d 2-135 mm and height h-300 mm is required to be processed.
Step 1, determining the outer diameter of the end head at the lower end of the mold core 4 and the inner diameter of the end head at the lower end of the upper mold 3:
with reference to FIGS. 4 and 5, the pipe has a medium diameter of
Figure BDA0001293729500000053
With reference to fig. 1, the outer diameter of the lower end of the mold core 4 is determined to be d 1-91 mm, and the inner diameter of the lower end of the upper mold 3 is determined to be d 2-135 mm.
Step 2, determining the diameter and height of the blank according to the equal volume principle of extrusion deformation:
according to the equal volume principle of extrusion deformation, the following characteristics are obtained: vE＝VC、VB＝VF；
Wherein the intermediate diameter of the wall thickness of the pipe is used as a boundary line, VEThe volume of the part inside the middle diameter of the cylindrical blank; vBThe volume of the part outside the middle diameter of the cylindrical blank; vCThe volume of the part inside the middle diameter of the extruded pipe; vFThe volume of the part outside the middle diameter of the extruded pipe;
according to VE＝VC、VB＝VFThe following can be obtained:
Figure BDA0001293729500000054
wherein h' is the height of the blank and D is the diameter of the blank;
substituting d1, d2, d and h to solve the equation set
Figure BDA0001293729500000062
Due to the allowance of the backward extrusion processing, the optimized blank size can be set to be a solid cylinder with the diameter of 168.2mm and the height of 108 mm.
Step 3, determining the outer diameter of the end head at the lower end of the upper die and the inner diameter of the lower die of the die according to the diameter and the height of the blank:
referring to fig. 1, the outer diameter of the lower end of the upper die 3 and the inner diameter of the lower die 5 are both 168.2 mm.
Step 4, determining the sizes of all parts of the upper die:
referring to fig. 3, the lower end of the upper mold 3 has a step of 1mm designed for facilitating demolding, the upper mold 3 is combined with the upper mold positioning plate 1, and therefore, a boss of 16mm in width and 20mm in height is designed at the upper end thereof, and since the pipe is formed between the upper mold and the mold core and is 300mm in height, the entire height of the upper mold 3 is 327 mm.
Step 5, determining the sizes of all parts of the positioning plate:
the positioning plate 1 is connected with the upper die 3 and the die core 4, and can be determined by combining the figure 1, the inner diameter of the upper die positioning plate 1 is 91mm, the outer diameter is 200mm, and the height is 70 mm. The lower end is provided with a boss with the height of 20mm and the outer diameter of 137 mm.
Step 6, determining the sizes of all parts of the mold core:
referring to fig. 4, the mold core 4 is connected to the upper mold positioning plate, the lower end of the upper mold positioning plate is provided with a step with a width of 0.5mm and a height of 45mm for facilitating demolding, and the total length of the mold core is 397 mm.
FIGS. 7(a) - (b) are comparative diagrams of AZ80 magnesium alloy tube with 22mm wall thickness backward extruded by a traditional backward extrusion die (front) and a backward extrusion die (back) designed by the method respectively; FIG. 7(a) the conventional reverse pressurizing mold is only directly extruded between a mold core and a lower mold, and is only extruded inside without considering the extrusion plastic deformation of the outer wall of the blank, so that the material of the outer wall cannot be supplied in time, and the outer wall of the pipe is cracked circumferentially for one circle; and (b) in the figure 7, the reverse extrusion die designed by the invention is adopted, and the actions among the die core, the upper die and the lower die are comprehensively utilized, so that the inner wall and the outer wall of the blank are simultaneously extruded, the product percent of pass is improved, and the obtained pipe is well formed.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, the protection scope of the present invention should be determined by the appended claims.

Claims (1)

1. A design method suitable for a backward extrusion die of a metal thick-wall pipe with poor plasticity is characterized by comprising the following steps:
step 1, determining the outer diameter of the end head at the lower end of a mold core and the inner diameter of the end head at the lower end of an upper mold according to the size requirement of a thick-wall pipe to be formed:
if the height of the pipe is h, the inner diameter is d1 and the outer diameter is d2, the intermediate diameter of the pipe is as follows:
Figure FDA0002224756890000011
① the outer diameter of the end head at the lower end of the mold core can be determined to be d1 according to the size of the pipe, and the inner diameter of the end head at the lower end of the upper mold is d 2;
step 2, determining the diameter and height of the blank according to the equal volume principle of extrusion deformation:
according to the equal volume principle of extrusion deformation, the following characteristics are obtained: vE＝VC、VB＝VF；
VEThe volume of the part inside the middle diameter of the cylindrical blank; vBThe volume of the part outside the middle diameter of the cylindrical blank; vCThe volume of the part inside the middle diameter of the extruded pipe; vFThe volume of the part outside the middle diameter of the extruded pipe;
according to VE＝VC、VB＝VFThe following can be obtained:
wherein h' is the height of the blank and D is the diameter of the blank;
substituting ① into ② and ③ to obtain:
Figure FDA0002224756890000013
Figure FDA0002224756890000014
the dimensions of the optimized blank thus determine that the blank is a solid cylinder with a diameter D and a height h';
step 3, determining the outer diameter of the end head at the lower end of the upper die and the inner diameter of the lower die of the die according to the diameter and the height of the blank:
namely, the outer diameter of the end head at the lower end of the upper die of the die is D, and the inner diameter of the lower die is D.
CN201710335621.9A 2017-05-12 2017-05-12 Reverse extrusion die suitable for blank thick-wall pipe with poor plasticity and design method Active CN108856328B (en)

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JP3936230B2 (en) * 2002-04-19 2007-06-27 日本特殊陶業株式会社 Manufacturing method of flanged tubular metal fittings
JP6047829B2 (en) * 2013-02-13 2016-12-21 住友電工焼結合金株式会社 Indirect extrusion method of Al alloy material
CN203862710U (en) * 2014-04-29 2014-10-08 重庆东轻铝合金锻造有限公司 Forged ring processing device
CN104014605B (en) * 2014-05-13 2016-06-15 盐城理研精密锻造有限公司 The equilateral reverse anti-extruding process of three-jaw flange sliding sleeve and reverse anti-extruding mold
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