AU2018441227A1

AU2018441227A1 - Method for shaping special pipe fitting having connection edge

Info

Publication number: AU2018441227A1
Application number: AU2018441227A
Authority: AU
Inventors: Xiaobo Fan; Zhubin He; Yanli Lin; Shijian Yuan
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2018-09-13
Filing date: 2018-09-13
Publication date: 2020-09-03
Also published as: WO2020051814A1

Abstract

A method for shaping a special pipe fitting having a connection edge, relating to the field of special pipe fitting shaping. First, an original pipe blank (4) having an integrated flange edge (4-2) is fixed on a mold (5, 6), the original pipe blank (4) adapting to the requirement for connection to an adjacent structure, and pre-deformation, i.e., bending or flattening, is performed on the original pipe blank, so as to deform the original pipe blank and the flange edge thereof so that the cross-sectional shape and bending axis of the pipe blank are approximate to those of a final part to obtain a pre-shaped pipe blank (5-3, 6-3); then the pre-shaped pipe blank is placed in a final shaping mold, the pre-shaped pipe blank is deformed under the effect of an internal pressure and an external load, i.e., an axial thrust, so that the pre-shaped pipe blank is attached to the mold and shaped to have bending axis and cross-sectional shape required to obtain the final special pipe fitting; the corresponding positions of the outside integrated flange and of a pipe wall are machined to obtain a connection hole required so as to complete machining. The present method has a simple process, high structural reliability and low manufacturing costs, and is a novel special pipe fitting shaping method.

Description

METHOD FOR FORMING SPECIAL PIPE WITH CONNECTING EDGE

Technical Field

The present invention belongs to the field of special pipe processing and

forming, and particularly relates to a method for forming a special pipe with a

connecting edge.

Background

In order to reduce the weight of a structure, many kinds of lightweight

components are needed in the fields such as aerospace, high-speed railway, vehicles

and bicycles. Generally speaking, the lightweight of components is realized in two

ways: the first is to optimize the structure, i.e. to adopt a structural form with more

reasonable bearing capacity and optimize the distribution of wall thickness, etc. in the

structure, so as to reduce the weight of the structure as far as possible on the premise

of ensuring the comprehensive performance of the structure; and the second is to

adopt lightweight materials with higher specific strength, such as aluminum alloy,

magnesium alloy and titanium alloy, which can greatly reduce the structural weight.

In terms of structural optimization, it is a very important way to adopt an

integral structure instead of a splicing structure. In recent years, internal

high-pressure forming technology has been widely used to realize the integral

forming of relatively long bending-axis structures. The technology generally uses a

pipe blank with a circular cross-section as an original blank, and adopts the

procedures such as bending, preforming and final forming to form an integral

complex bending-axis pipe structure. For example, a U-shaped sub-frame on the

chassis of an automobile is manufactured by a circular cross-section pipe blank through the solution of CNC bending, flattening preforming and internal high-pressure shaping, which is used to replace a U-shaped sub-frame manufactured by piecewise welding and has achieved obvious weight reduction effect.

However, the U-shaped sub-frame that is integral in axial direction is not used

alone, and need to be connected with adjacent chassis structural components and the

engine, therefore a plurality of connecting platforms and connecting holes need to be

provided on/in the integral sub-frame, then a plurality of connecting plates are

connected with the integral sub-frame, and the connecting plates are additionally

connected with other structures. The number of connecting plates on a U-shaped

sub-frame is often as much as 20 and the weight is about 10 kg, which somewhat

weakens the weight reduction effect of adopting an integral sub-frame. Moreover, in

order to realize reliable connection with the connecting plates, it is necessary to

preform a plurality of local structures on the integral sub-frame; the diameter and

radius of curvature of the local structures are often very different from those of

adjacent areas, which inevitably increases the difficulty of forming the integral

sub-frame, especially easily leads to the deterioration of the dimensional accuracy

and consistency of the integral sub-frame, and further leads to high difficulty, low

welding accuracy and low reliability in assembling the integral sub-frame.

In order to solve the problem that the existing special pipes need to be added

with additional connecting units (such as a plurality of connecting plates) when

connected and fixed with other structures, which leads to the increase of structural

weight, the deterioration of structural integrity and reliability, the difficulty in

welding and riveting in a narrow space, and the difficulty in guaranteeing dimensional accuracy and reliability, it is necessary to develop a new special pipe and a forming method thereof.

Summary

The present invention provides a method for forming a special pipe with a

connecting edge in order to solve the problem that the existing special pipe need to be

added with a plurality of complex shape connecting plates to realize the fixation and

connection with other structures, which leads to complex procedures, low structural

reliability and high manufacturing cost.

The technical solution of the present invention is:

A method for forming a special pipe with a connecting edge, comprising the

following steps:

Step 1: designing/selecting or processing an original pipe blank with an outside

integrated flange according to the requirements for connecting a special pipe with an

adjacent structure;

Step 2: fixing the original pipe blank with an outside integrated flange on a

preforming mould, and using the flange to position and constrain the original pipe

blank;

Step 3: closing the preforming mould, and predeforming the original pipe blank

by bending or flattening to make the original pipe blank and the flange thereof

deformed to a cross-section shape and bending axis close to a final part to obtain a

preformed pipe blank;

Step 4: placing the preformed pipe blank in a final forming mould, and using the

flange to position and constrain the preformed pipe blank;

Step 5: closing the final forming mould, deforming the preformed pipe blank

under the external loads of internal pressure and axial thrust, and making the

preformed pipe blank stick to the mould to form required bending axis and

cross-section shape to obtain a final special pipe; and

Step 6: taking out the final special pipe, and machining corresponding positions

of the outside integrated flange and pipe wall to obtain required connecting holes and

finish the processing of a special pipe with an integrated connecting edge.

The original pipe blank is an extruded section or a plate bending section; when

the original pipe blank is an extruded section, no welding seam is formed between the

special pipe and the flange of the original extruded section, and the material is

aluminum alloy or magnesium alloy; when the original pipe blank is a plate bending

section, the edge of the plate blank on one side of the special pipe is butt joined or

overlapped with the connecting edge to form a closed special cross-section; and the

overlapping mode is external overlapping or internal overlapping.

In step 2, when fixing the original pipe blank on the preforming mould, the

positioning mode is: inserting the flange of the original pipe blank into a groove in

the mould, or using a split mould to clamp the flange.

In step 3, a support is placed in the special pipe before predeforming the original

pipe blank by bending or flattening; when the support is solid, the yield strength of

the solid support is 30-200 MPa lower than that of the special pipe; and when the

support is fluid, the pressure of the fluid support is 10-100 MPa. The solid support is

a rubber or polyurethane rod.

In step 5, when the working temperature of the final forming mould is normal temperature, the preformed pipe blank is filled with water, oil or mixture of water and oil; and when the working temperature of the final forming mould is 300°C-650°C, the preformed pipe blank is filled with high-pressure air, nitrogen or argon, and the gas pressure is 5-70 MPa.

The present invention has the following beneficial effects:

(1) In the method for forming a special pipe with a connecting edge of the

present invention, the original blank adopted has an integrated flange, the special

cross-section pipe and the flange are deformed at the same time and always remain

integrated, and the special pipe is connected with other structures through the

connecting edge, which avoids forming complex connecting bosses or fixing holes

on/in the main body of the special pipe, and thus can greatly simplify the shape

complexity of the main body of the special pipe and reduce the manufacturing cost;

(2) In the method for forming a special pipe with a connecting edge of the

present invention, the original blank adopted has an integrated flange, and the special

integrated, which avoids the difficult problems easy to occur when welding or

riveting independent connecting plates on an already formed special pipe (with a

bending axis or special cross-section), e.g. the connecting plates and the special pipe

are difficult to be positioned in space, the welding quality and consistency are poor,

and connection cannot be realized in a local narrow position;

(3) In the method for forming a special pipe with a connecting edge of the

cross-section pipe and the flange are deformed at the same time and always remain integrated, the structure between the connecting edge and the main body of the special pipe is compact and has good integrity, and an external structure can be directly connected with the flange without the need of arranging connecting plates or local reinforcing structures at the connecting position of the special cross-section pipe, so the weight of the components is obviously reduced;

(4) In the method for forming a special pipe with a connecting edge of the

integrated, so the welding seam between the connecting plates and the special pipe

when adopting a split-type structure is eliminated, and the overall mechanical

property, fatigue resistance and corrosion resistance of the components are obviously

increased;

(5) In the method for forming a special pipe with a connecting edge of the

integrated, which avoids the problems that complex thermal deformation occurs in

the welding process of the connecting plates and the special pipe, and the accuracy of

the special pipe and the assembly accuracy with other structures are affected when

adopting a split-type structure;

(6) In the method for forming a special pipe with a connecting edge of the

integrated; because the shape of the integrated connecting edge is relatively simple and the surrounding structures are generally unhindered, different forms of connecting structures can be conveniently and flexibly processed on the connecting edge, which provides the possibility for realizing various forms of local connection;

(7) In the method for forming a special pipe with a connecting edge of the

integrated, the original blank with a flange can be produced either by extrusion or by

rolling, the manufacturing cost of the original blank is low, and no complex mould

tooling need to be added when forming the special pipe subsequently, so the

manufacturing cost of the special pipe with an integrated connecting edge is lower

than that of a traditional structure;

(8) In the method for forming a special pipe with a connecting edge of the

integrated, and the special cross-section pipe and the flange can be welded to form a

special cross-section pipe cavity with a closed cross-section first and then be

processed by subsequent forming, or be not welded into a closed special cross-section

pipe cavity first but fixed and reinforced by spot welding and other methods after

forming.

Description of Drawings

Fig. 1 is a schematic diagram of an integral special cross-section pipe of the

present invention.

Fig. 2 is a schematic diagram of an integral special cross-section pipe of the present invention connected with an adjacent structure through a connecting plate.

Fig. 3 is a schematic diagram of a special pipe with a connecting edge of the

present invention (a final part).

Fig. 4 is a schematic diagram of a special cross-section pipe and a flange

manufactured by extrusion of the present invention, wherein (a-1) and (a-2) are a

special pipe with a circular cross-section and a cross-sectional view thereof, (b-1) and

(b-2) are a special pipe with a square cross-section and a cross-sectional view thereof,

and (c-1) and (c-2) are a special pipe with a triangle cross-section and a

cross-sectional view thereof.

Fig. 5 is a schematic diagram of forming a special pipe with a connecting edge

of the present invention, wherein an original blank is manufactured by extrusion,

comprising three main procedures: bending, preforming and internal pressure bulging;

(a) is to predeform by bending, (b) is to predeform by flattening, and (c) is to

predeform by internal pressure bulging.

Fig. 6 is a schematic diagram of a special cross-section pipe and a flange

manufactured by plate bending of the present invention (an initially welded and

closed special cross-section pipe in edge butt joint mode), wherein (a) is a circular

cross-section, (b) is a square cross-section with a connecting edge on one side, and (c)

is a square cross-section with a connecting edge in the middle.

Fig. 7 is a schematic diagram of a special cross-section pipe and a flange

manufactured by plate bending of the present invention (an initially welded special

cross-section pipe in internal overlapping mode), wherein (a) is a circular

cross-section, (b) is a square cross-section with a connecting edge on one side, and (c) is a square cross-section with a connecting edge in the middle.

Fig. 8 is a schematic diagram of a special cross-section pipe and a flange

cross-section pipe in external overlapping mode), wherein (a) is a circular

is a square cross-section with a connecting edge in the middle.

Fig. 9 is a schematic diagram of forming a special pipe with a connecting edge

of the present invention using a mould for compressing and sealing, wherein (a) is a

solid-medium pipe without a sealing ring, and (b) is a fluid-medium pipe with a

sealing ring.

Fig. 10 is a schematic diagram of forming a special pipe with a connecting edge

of the present invention using a split mould (the split mould is used during the

preforming and final forming of the special pipe and the connecting edge).

In the figures: 1 integral special cross-section pipe; 2 connecting plate; 3 special

cross-section pipe with a connecting edge; 3-1 special cross-section pipe; 3-2

connecting edge; 3-3 connecting hole; 4 special cross-section original pipe blank with

a flange; 4-2 flange; 5 bending mould; 5-1 bending preforming upper mould; 5-2

bending preforming lower mould; 5-3 bending preformed pipe blank; 6 preforming

mould; 6-1 flattening preforming upper mould; 6-2 flattening preforming lower

mould; 6-3 flattening preformed pipe blank; 7 internal pressure bulging mould; 7-1

internal pressure bulging upper mould; 7-2 internal pressure bulging lower mould;

7-3 internal pressure bulged pipe blank; 8 welding seam (initial pipe blank already

welded); 8-1 butt joint welding seam; 8-2 internal overlapping welding seam; 8-3 external overlapping welding seam; 9 compressing and sealing mould; 10 solid medium; 11 liquid medium; 12 sealing ring/strip (not welded initially, but used for sealing during preforming or internal pressure bulging).

Detailed Description

The technical solution of the present invention is further described below in

combination with specific embodiments and drawings.

Embodiment 1: a method for forming a special pipe with a connecting edge of

the present invention is realized by the following steps:

Step 1: designing/selecting/processing an original pipe blank with an outside

adjacent structure;

Step 2: fixing the original pipe blank with an outside integrated flange on a

blank;

step 3: predeforming the original pipe blank by bending or flattening to make the

original pipe blank and the flange thereof deformed to a cross-section shape and

bending axis close to a final part;

step 4: placing the predeformed pipe blank with a flange in a final forming

mould, and using the flange to position and constrain the preformed pipe blank;

step 5: closing the final forming mould, deforming the preformed pipe blank

under the external loads such as internal pressure and axial thrust, and making the

pipe blank stick to the mould to form required bending axis and cross-section shape;

and

of the outside integrated flange and pipe wall to obtain required connecting holes, etc.,

and obtain a finally required special pipe with an integrated connecting edge.

[The following is the mode of adopting an extruded section]

Embodiment 2: a method for forming a special pipe with a connecting edge of

the present invention, characterized in that in step 1, the original pipe blank adopted

is an extruded section, and the material is aluminum alloy or magnesium alloy. No

welding seam is formed between the special pipe and the flange of the original

extruded section. Others are the same as those in embodiment 1.

The embodiment has the following beneficial effects: the special pipe and the

flange of the original pipe blank are formed in one time during the extrusion process,

and the special pipe and the flange will always remain integrated in the subsequent

deforming process, so the connection between the special pipe and the connecting

edge can be realized without using the methods such as welding before or after part

forming.

Embodiment 3: a method for forming a special pipe with a connecting edge of

the present invention, characterized in that in step 2, the original pipe blank is fixed

and positioned on the forming mould by inserting the flange of the original pipe

blank into a groove in the mould, or using a split mould to clamp the flange. Others

are the same as those in embodiment 1.

The embodiment has the following beneficial effects: as the special pipe and the

flange of the original pipe blank are integrated, when the flange is clamped and fixed,

unreasonable rotation along the central axis of the special pipe in the subsequent bending or flattening predeforming process can be restricted, thus the cross-section shape and axis shape of the special pipe after bending or flattening predeforming can be effectively controlled, and uncontrollable deformation of the special pipe during the predeforming process can be avoided from affecting the subsequent internal pressure bulging.

Embodiment 4: a method for forming a special pipe with a connecting edge of

the present invention, characterized in that in step 3, a solid support such as a rubber

or polyurethane rod is placed, or a fluid support such as gas or liquid is filled in the

special pipe before predeforming such as by bending or flattening. The yield strength

of the solid support is 30-200 MPa lower than that of the special pipe, and the

pressure of the fluid support is 10-100 MPa. Others are the same as those in

embodiments 1 and 2.

The embodiment has the following beneficial effects: as the special pipe has a

closed structure, it is easy to establish a certain supporting pressure in the special pipe.

Under the support of internal pressure, the special pipe can undergo complex bending

or flattening deforming without producing predeformations that are disadvantageous

to the subsequent bulging, such as local folding and cracking or abnormal

cross-section indentation, thus providing guarantee for obtaining a final special pipe

by subsequent internal bulging.

Embodiment 5: a method for forming a special pipe with a connecting edge of

the present invention, characterized in that in step 5, the final forming mould adopted

is at normal temperature, and the preformed pipe blank is filled with water, oil or

mixture of water and oil; or the final forming mould adopted is in heated state at

300°C-650C, the preformed pipe blank is filled with high-pressure air, nitrogen or

argon, and the gas pressure is 5-70 MPa. Others are the same as those in

embodiments 1 and 2.

The embodiment has the following beneficial effects: a reasonable mould

temperature is selected for subsequent deforming according to the difference between

the preformed pipe blank and the final mould cavity. When the difference is relatively

small and no local structure with a fillet radius of less than 1.5 times the thickness of

the pipe wall is provided on the mould cavity, deforming can be carried out at normal

temperature; when the difference is relatively large or a local structure with a fillet

radius of less than 1.5 times the thickness of the pipe wall is provided on the mould

cavity, the mould can be heated to an appropriate temperature (350°C-550 0 C for 6061

aluminum alloy, and 280°C-500 0C for AZ31 magnesium alloy) before forming.

Therefore, the problems of early cracking or insufficient filling of local small fillets

during forming at an unreasonable temperature are avoided.

[The following is the mode of adopting a plate bending section]

Embodiment 6: a method for forming a special pipe with a connecting edge of

the present invention, characterized in that in step 1, the original blank adopted is a

special cross-section section with a flange obtained by plate bending. The edge of the

plate blank on one side of the special pipe is butt joined with the special pipe or the

connecting edge to form a closed special cross-section. Others are the same as those

in embodiment 1.

The embodiment has the following beneficial effects: since the edge of the plate

blank on one side of the special pipe is directly butt joined with the plate blank to form a closed cross-section, and no excess transition material is used between the special cross-section pipe and the flange, the original blank in this form weighs the least, the preparation process thereof is similar to that of the traditional circular cross-section pipe blank, and the cost is relatively low.

Embodiment 7: a method for forming a special pipe with a connecting edge of

plate blank on one side of the special pipe is overlapped with the special pipe or the

flange to form a closed special cross-section. Others are the same as those in

embodiment 1.

The embodiment has the following beneficial effects: the edge of the plate blank

on one side of the special pipe is overlapped with the plate blank to form a closed

cross-section, and the overlapping position can be located either on the special pipe

or on the flange; the overlap edge can either be pre-welded with the special

pipe/flange before subsequent forming, or be preformed such as by bending or

flattening before welding and final internal pressure bulging; and it is also possible to

realize sealing between the overlap edge and the special pipe/flange by mould

compressing during bulging, and then decide whether to carry out spot weld or full

weld as required after final forming. By means of overlapping, reasonable

connection/constraint between the special pipe and the flange can be realized as

required, which provides more possibilities for the reasonable control of material

deformation in the processes of preforming and final internal pressure bulging.

Embodiment 8: a method for forming a special pipe with a connecting edge of the present invention, characterized in that in step 2, the flange of the original pipe blank is processed to obtain the required connecting holes or connecting structures before fixing the original pipe blank in the mould. Others are the same as those in embodiment 1.

The embodiment has the following beneficial effects: when the connecting holes

or connecting structures are processed directly on the flange of the original pipe blank,

because the flange is in flat form, the flange is easy to install and clamp during

machining and the machining equipment used is simple. When the final special pipe

with an integrated connecting edge is relatively simple, and no drastic cross-section

change or axis distortion will occur in the processes of preforming and final internal

pressure bulging, the application of this solution can greatly improve the efficiency

and reduce the cost.

Embodiment 9: a method for forming a special pipe with a connecting edge of

the present invention, characterized in that in steps 2 and 4, the preforming mould

and the final forming mould adopt split structures, the flange on the original or

preformed pipe blank is positioned and constrained by an independent module, and

another independent module is used as the forming mould for the special pipe. Others

are the same as those in embodiment 1.

The embodiment has the following beneficial effects: since the flange is

positioned and constrained by an independent module, the

positioning/constraint/deforming of the flange will be independent of the subsequent

mould closing, loading and deforming processes of the special pipe, and no mutual

effect will be produced. When the connecting edge and the special pipe on the final part have relatively large difference in deforming degree and deforming mode, the deforming of the flange and the special pipe can be realized more precisely by adopting the two independent modules of this embodiment. At the same time, the requirements for mould design and processing as well as equipment control are also greatly reduced.

Claims

CLAIMS:

1. A method for forming a special pipe with a connecting edge, comprising the

following steps:

adjacent structure;

step 2: fixing the original pipe blank with an outside integrated flange on a

blank;

step 3: closing the preforming mould, and predeforming the original pipe blank

by bending or flattening to make the original pipe blank and the flange thereof

preformed pipe blank;

flange to position and constrain the preformed pipe blank;

step 5: closing the final forming mould, deforming the preformed pipe blank

under the external loads of internal pressure and axial thrust, and making the

preformed pipe blank stick to the mould to form required bending axis and

cross-section shape to obtain a final special pipe;

finish the processing of a special pipe with an integrated connecting edge.

2. The method for forming a special pipe with a connecting edge of claim 1, wherein

the original pipe blank is an extruded section or a plate bending section; when the

original pipe blank is an extruded section, no welding seam is formed between the

overlapping mode is external overlapping or internal overlapping.

3. The method for forming a special pipe with a connecting edge of claim 1 or 2,

wherein in step 2, when fixing the original pipe blank on the preforming mould, the

the mould, or using a split mould to clamp the flange.

4. The method for forming a special pipe with a connecting edge of claim 1 or 2,

wherein in step 3, a support is placed in the special pipe before predeforming the

original pipe blank by bending or flattening; when the support is solid, the yield

strength of the solid support is 30-200 MPa lower than that of the special pipe; when

the support is fluid, the pressure of the fluid support is 10-100 MPa; and the solid

support is a rubber or polyurethane rod.

5. The method for forming a special pipe with a connecting edge of claim 3, wherein

in step 3, a support is placed in the special pipe before predeforming the original pipe

blank by bending or flattening; when the support is solid, the yield strength of the

solid support is 30-200 MPa lower than that of the special pipe; when the support is

fluid, the pressure of the fluid support is 10-100 MPa; and the solid support is a rubber or polyurethane rod.

6. The method for forming a special pipe with a connecting edge of claim 1, 2 or 5,

wherein in step 5, when the working temperature of the final forming mould is

normal temperature, the preformed pipe blank is filled with water and/or oil; and

when the working temperature of the final forming mould is 300°C-650°C, the

preformed pipe blank is filled with high-pressure air, nitrogen or argon, and the gas

pressure is 5-70 MPa.

7. The method for forming a special pipe with a connecting edge of claim 3, wherein

in step 5, when the working temperature of the final forming mould is normal

temperature, the preformed pipe blank is filled with water and/or oil; and when the

working temperature of the final forming mould is 300°C-650°C, the preformed pipe

blank is filled with high-pressure air, nitrogen or argon, and the gas pressure is 5-70

MPa.

8. The method for forming a special pipe with a connecting edge of claim 4, wherein

in step 5, when the working temperature of the final forming mould is normal

MPa.

Fig. 1

Fig. 2

Fig. 3 1/5

(a-1) (a-2)

(b-1) (b-2)

(c-1) (c-2)

Fig. 4

(a) (b) (c)

Fig. 5 2/5

(a) (b) (c)

Fig. 6

(a) (b) (c)

Fig. 7

3/5

(a) (b) (c)

Fig. 8

(a) (b)

Fig. 9

4/5

Fig. 10

5/5