U.S. patent application number 13/836822 was filed with the patent office on 2014-09-18 for pressure sequence process for hydro-forming an extruded structural tube.
This patent application is currently assigned to FORD GLOBAL TECHNOLOGIES, LLC. The applicant listed for this patent is FORD GLOBAL TECHNOLOGIES, LLC. Invention is credited to S. George Luckey, Jr., Kiran Kumar Mallela.
Application Number | 20140260479 13/836822 |
Document ID | / |
Family ID | 51419316 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140260479 |
Kind Code |
A1 |
Luckey, Jr.; S. George ; et
al. |
September 18, 2014 |
PRESSURE SEQUENCE PROCESS FOR HYDRO-FORMING AN EXTRUDED STRUCTURAL
TUBE
Abstract
A pressure sequence hydro-forming method is used to form an
extruded structural tube. The extruded structural tube is placed in
a hydro-forming die that is partially closed to compress the tube.
The tube is filled with a hydro-forming liquid at a first pressure.
The hydro-forming die is then closed and the pressure of the
hydroforming fluid is increased as the hydro-forming die is fully
closed. The pressure is increased to a second level of pressure to
shape the tube into the desired part shape.
Inventors: |
Luckey, Jr.; S. George;
(Dearborn, MI) ; Mallela; Kiran Kumar;
(Northville, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FORD GLOBAL TECHNOLOGIES, LLC |
Dearborn |
MI |
US |
|
|
Assignee: |
FORD GLOBAL TECHNOLOGIES,
LLC
Dearborn
MI
|
Family ID: |
51419316 |
Appl. No.: |
13/836822 |
Filed: |
March 15, 2013 |
Current U.S.
Class: |
72/61 |
Current CPC
Class: |
B21C 23/085 20130101;
Y10T 29/49805 20150115; B21D 26/033 20130101 |
Class at
Publication: |
72/61 |
International
Class: |
B21D 26/033 20060101
B21D026/033 |
Claims
1. A method of forming an extruded structural tube to form a part
comprising: loading the extruded structural tube into a
hydro-forming die; partially closing the hydro-forming die; filling
the extruded structural tube with a liquid beginning at a first
pressure; closing the hydro-forming die with the tube disposed in
the hydro-forming die; and increasing the level of pressure applied
to the liquid to a second level of pressure to shape the extruded
structural tube.
2. The method of claim 1 further comprising the step of pre-bending
the extruded structural tube that is longitudinally bent in a
bending tool to form a pre-bent tube before loading the
hydro-forming die.
3. The method of claim 2 further comprising pre-forming the
pre-bent tube in a pre-forming die.
4. The method of claim 1 wherein the step of increasing the level
of pressure further comprises increasing the level of pressure
beginning with the step of filling the extruded structural tube and
wherein the level of pressure is gradually increased to the second
level in the hydro-forming die resulting in the extruded structural
tube being hydro-formed into the die.
5. The method of claim 1 wherein the step of increasing the level
of pressure within the extruded structural tube in the
hydro-forming die further comprises hydro-piercing the extruded
structural tube.
6. A method of forming a part comprising: extruding an aluminum
alloy to form an extruded structural tube; bending the tube
longitudinally in a bending operation; pre-forming the tube
laterally in a pre-form die; loading the tube into a hydro-forming
die; partially closing the hydro-forming die to radially compress
the tube; filling the tube with a liquid at a first level of
pressure; closing the hydro-forming die to radially compress the
tube; and increasing the level of pressure applied to the liquid to
a second level of pressure to shape the tube to form the part.
7. The method of claim 6 wherein the extruding step further
comprises extruding heated aluminum through an extrusion die
including a mandrel plate that separates the heated aluminum and a
cap section that re-converges the heated aluminum to form the
extruded structural tube with a plurality of weld lines being
formed where the heated aluminum re-converges.
8. The method of claim 7 wherein the extrusion die is a porthole
die.
9. The method of claim 6 further comprising pre-bending the
extruded structural tube in a rotary draw bending tool before the
loading step.
10. The method of claim 6 wherein the first level of pressure is a
closing pressure and the second level of pressure is a calibration
pressure.
11. The method of claim 6 wherein the step of increasing the level
of pressure within the tube in the hydro-forming die results in the
tube being hydro-formed into the die.
12. The method of claim 11 wherein the step of increasing the level
of pressure within the tube in the hydro-forming die further
comprises hydro-piercing the tube.
13. The method of claim 6 further comprising heating the part after
forming to artificially age the aluminum alloy.
14. A method of forming a part comprising: extruding an aluminum
alloy through a porthole die to form an extruded structural tube;
cutting the tube; pre-bending the tube to form a pre-bent tube;
loading the pre-bent tube into a pre-forming die; closing the
pre-forming die partially to radially compress the pre-bent tube to
form a pre-bent/pre-formed tube; filling the pre-bent/pre-formed
tube with a liquid that is under a first level of pressure; closing
the hydro-forming die completely; and increasing the level of
pressure applied to the liquid to a second level of pressure that
is greater than the first level of pressure to shape the
pre-bent/pre-formed tube.
15. The method of claim 14 wherein the extruding step further
comprises extruding heated aluminum through an extrusion die
including a mandrel plate that separates the heated aluminum and a
cap section that re-converges the heated aluminum to form the
extruded structural tube with a plurality of weld lines being
formed where the heated aluminum re-converges.
16. The method of claim 14 wherein the step of pre-bending the
pre-bent/pre-formed tube is performed in a bending tool before the
loading step.
17. The method of claim 14 wherein the step of increasing the level
of pressure further comprises increasing the level of pressure
beginning with the step of filling the pre-bent tube and wherein
the level of pressure is gradually increased to the second
level.
18. The method of claim 14 wherein the step of increasing the level
of pressure with the pre-bent/pre-formed tube in the hydro-forming
die results in hydro-forming the pre-bent/pre-formed tube into the
hydro-forming die.
19. The method of claim 18 wherein the step of increasing the level
of pressure within the pre-bent/pre-formed tube in the
hydro-forming die further comprises hydro-piercing the tube.
20. The method of claim 14 further comprising heating the part
after forming to artificially age the aluminum alloy.
Description
TECHNICAL FIELD
[0001] Extruded structural tubes are extruded through a die, cut to
size and formed in a hydro-forming process.
BACKGROUND
[0002] Vehicle manufacturers are implementing lighter, stronger
materials, such as aluminum alloys to meet emission reduction
goals, meet fuel economy goals, reduce manufacturing costs, and
reduce vehicle weight. Increasingly demanding safety standards must
be met while reducing vehicle weight. One approach to meeting these
competing interests and objectives is to hydro-form high strength
aluminum alloy tubular blanks into strong, lightweight hydro-formed
parts.
[0003] Aluminum tube types include seam-welded tube, extruded
seamless tube, and extruded structural tube. Seam-welded tube and
extruded seamless tube are expensive. Seam-welded tubes and
extruded seamless tubes are expensive to convert to finished
hydro-formed parts. Extruded structural tubes are lower in cost
because they are formed in a continuous mill operation having a
greater line and material utilization efficiency than extruded
seamless tubes and seam-welded tubes.
[0004] Extruded structural tubes are formed by extruding an
aluminum billet through an extrusion die at a high temperature and
at high pressure. Discontinuous material flow across the section of
the shape occurs when the flowing aluminum separates in the mandrel
plate and re-converges in the cap section. A weld line, or joining
line, is created where the flowing aluminum re-converges to form
the extruded shape. Extruded structural tubes may have two or more
weld lines that are an artifact of the porthole extrusion
process.
[0005] Hydro-forming complex parts may require a series of bending,
pre-forming, hydro-forming, piercing and machining operations.
Bending and hydro-forming aluminum tubes is not currently in use in
high volume production operations. (i.e. more than 100,000
units/year) Aluminum intensive vehicles (AIVs) are envisioned that
use metal forming methods consistent with current conventional
automotive manufacturing methods.
[0006] In a high pressure hydro-forming (HPH) operation, the tube
is inserted in the HPH die before any fluid under pressure is
provided inside the tube. The dies are closed that can result in
buckling the tube's cross-section. High pressure incompressible
hydro-forming fluid, such as water, is supplied to expand and shape
the tube to conform to the die cavity. Substantial press tonnage is
required to hydro-form parts in HPH processes. Substantial
expansion of the tube (circumferential length of line expansion of
more than 5%) is necessary to eliminate any tube buckles and
produce complexly shaped parts. It is not feasible to form most
parts from aluminum tubes with high expansion HPH operations
because aluminum seam-welded, seamless tubes and structural
extrusion tubes are less formable than mild steel tubes.
[0007] The above challenges and other challenges are addressed by
this disclosure as summarized below.
SUMMARY
[0008] According to one aspect of this disclosure, a method is
disclosed for forming an extruded structural tube to form a part.
The extruded structural tube is first loaded into a hydro-forming
die. The hydro-forming die is partially closed and the extruded
structural tube is filled with a liquid beginning at a first
pressure. The hydro-forming die is then closed with the tube
disposed in the hydro-forming die. The level of pressure applied to
the liquid is increased to a second level of pressure to shape the
extruded structural tube to form the part.
[0009] The extruded structural tube may be pre-bent along its
length in a rotary draw bending operation or a push roll bending
operation and may be pre-formed radially in a pre-forming die. The
pre-bending and pre-forming steps precede loading the
pre-bent/pre-formed tube into the hydro-forming die. The
hydro-forming die cavity has a shape with a circumferential
perimeter that is less than or equal to 2% greater than the
circumferential perimeter of the extruded structural tube.
[0010] According to a further aspect of this disclosure, a method
of forming a part comprises extruding an aluminum alloy through a
porthole die to form an extruded structural tube. The tube is cut
to the desired size and is bent to form a pre-bent tube. The
pre-bent tube may be bent in either a rotary draw bending operation
or in a push roll bending operation. (As used herein, the term
"bending operation" should be understood and interpreted as
referring to in either a rotary draw bending operation or in a push
roll bending operation.) The pre-bent and pre-formed tube is loaded
into a hydro-forming die that is partially closed to radially
compress the pre-bent and pre-formed tube. The pre-bent and
pre-formed tube is placed in a hydro-forming die and filled with a
liquid at a first level of pressure. The hydro-forming die is
closed completely and the level of pressure applied to the liquid
is increased to a second level of pressure that is greater than the
first level of pressure to shape the pre-bent and pre-formed tube
into the part.
[0011] According to another aspect of this disclosure, a method of
forming a part from an extruded structural tube is disclosed that
begins with extruding an aluminum alloy to form the extruded
structural tube. The tube is pre-bent in a bending operation to
form a pre-bent tube. The pre-bent tube is then loaded into a
pre-forming die and the pre-forming die radially compresses the
tube to form a pre-bent/pre-formed tube. The pre-bent/pre-formed
tube is filled with a liquid at a first level of pressure as the
hydro-forming die is partially closed. The hydro-forming die is
then fully closed against the pre-bent/pre-formed tube and the
level of pressure of the liquid is increased to a second level of
pressure to shape the tube.
[0012] According to other aspects of this disclosure that may be
combined with any of the above described methods, the extruding
step may further comprise extruding aluminum at a billet
temperature greater than 450.degree. C. and less than 600.degree.
C. through an extrusion die including a mandrel plate that
separates the heated aluminum and a cap section that re-converges
the heated aluminum to form the extruded structural tube with a
plurality of weld lines being formed where the heated aluminum
re-converges. The extrusion die may be a porthole die which may
also be referred to as an extruded structural tube die.
[0013] According to another aspect of this disclosure that may be
combined with any of the above described methods, the step of
pre-bending the extruded structural tube is a bending operation
that may be performed in a rotary draw bending tool or a push-roll
bending tool.
[0014] According to other aspects of this disclosure that may be
combined with any of the above described methods, the step of
increasing the level of pressure may further comprise increasing
the level of pressure beginning with the step of filling the tube
and wherein the level of pressure is gradually increased to the
second level. The first level of pressure may be referred to as a
closing pressure and the second level of pressure may be referred
to as a calibration pressure. The step of increasing the level of
pressure within the tube in the hydro-forming die results in the
tube being hydro-formed into the die. The step of increasing the
level of pressure within the tube in the hydro-forming die may
further comprise hydro-piercing the tube.
[0015] The above aspects of this disclosure and other aspects will
be described in greater detail below with reference to the attached
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a flowchart illustrating one example of a pressure
sequence hydro-forming process for extruding a structural tube;
[0017] FIG. 2 is an exploded perspective view of a porthole
die;
[0018] FIG. 3 is a diagrammatic representation of a rotary draw
bending tool pre-forming a portion of a tube;
[0019] FIG. 4 is a diagrammatic cross-sectional view of a
pre-formed tube in a pre-forming die;
[0020] FIG. 5 is a diagrammatic cross-sectional view of the
pre-forming die radially compressing the pre-bent/pre-formed
tube;
[0021] FIG. 6 is a diagrammatic cross-sectional view of the tube
filled with a liquid in a hydro-forming die under a first level of
pressure;
[0022] FIG. 7 is a diagrammatic cross-sectional view of the
hydro-forming die being completely closed over the
pre-bent/pre-formed tube under a second level, or calibration level
of pressure; and
[0023] FIG. 8 is a partial cross-section view of a tube that is
being hydro-pierced with a hydro-piercing punch.
DETAILED DESCRIPTION
[0024] A detailed description of the illustrated embodiments of the
present invention is provided below. The disclosed embodiments are
examples of the invention that may be embodied in various and
alternative forms. The figures are not necessarily to scale. Some
features may be exaggerated or minimized to show details of
particular components. The specific structural and functional
details disclosed in this application are not to be interpreted as
limiting, but merely as a representative basis for teaching one
skilled in the art how to practice the invention.
[0025] Referring to FIGS. 1 and 2, one example of a process for
hydro-forming an extruded structural tube is illustrated. The
process begins by forming an extruded structural tube in a porthole
die at 12. Referring to FIG. 2, one example of a porthole extrusion
die 14 is illustrated. The porthole extrusion die 14 includes a
mandrel plate 16 and a cap section 18. An aluminum billet 20 is
heated and extruded through the porthole extrusion die 14. The
aluminum billet 20 is extruded at high temperature and pressure
through the extrusion die 14. The extruded aluminum is separated in
the mandrel plate 16 and re-converges in the cap section 18. The
point that the aluminum re-converges creates weld lines 26 in the
extruded tube 22. The extruded tube 22 may be referred to as a
structural extruded tube. The extruded tube 22 is formed in a
continuous mill operation.
[0026] Referring to FIGS. 1 and 3, the extruded, or structural,
tube 22 is cut to length at 30. As shown in FIG. 3, the tube is
then pre-formed at 32 in a rotary draw bending tool 34.
[0027] Referring to FIGS. 1 and 4, the pre-formed tube 36 is loaded
at 38 into a pre-form die 39. As shown in FIG. 4, the pre-formed
tube 36 is loaded into the pre-form die 39 that is illustrated as a
two-part die 39, but could be a die having more than two parts.
[0028] Referring to FIGS. 1 and 5, the next step in the process is
to partially close the pre-form die 39 to radially compress the
pre-formed tube at 42. Referring specifically to FIG. 5, the
pre-formed tube 36 (shown in FIG. 4) is illustrated as it is
compressed in the pre-form die 39 to form a pre-bent/pre-formed
tube 44.
[0029] Referring to FIGS. 1 and 6, the next step in the process is
to fill the tube in a hydro-forming die 40 with a liquid under a
first level of pressure. The first level of pressure is within the
range of 50 to 200 bar with a nominal pressure being 100 bar. This
is illustrated in FIG. 6 in which the pre-bent/pre-formed tube 44
is filled with a hydro-forming liquid 48, such as water. The
pre-bent/pre-formed tube 44 is shown to be more compressed in FIG.
6 in comparison to its condition in FIG. 5.
[0030] Referring to FIGS. 1, 7 and 8, the next step in the process
is to completely close the hydro-forming die at 50. Referring to
FIG. 7, the hydro-forming die 40 is shown completely closed with
the fully formed part 52 conforming to the die and with the liquid
48 filling the fully formed part 52. Referring back to FIG. 1, the
process continues by increasing the level of pressure of the liquid
to a second level to form and hydro-pierce the part at 54. The
second level of pressure is within the range of 750 to 2,000 bar
with a nominal pressure of 1,000 bar.
[0031] Referring to FIG. 8, the fluid formed part 52 is shown in
isolation with a hydro-formed punch 56. The hydro-formed punch 56
may be incorporated as part of the hydro-formed die 40 to punch a
hole 58 in the part 52 during the hydro-forming process in the
hydro-forming die 40. A slug 70 is partially separated from the
part 52 when the hole 58 is formed.
[0032] Referring to FIG. 1, the part may be trimmed at 64 and, as
indicated, the trimming operation may be a laser trimming
operation. It should be understood that other types of trimming
operations may be used instead of laser trimming. Following the
laser trimming operation, the part may be heat treated to
artificially age the aluminum alloy at 66. The part may then be
subjected to batch pretreatment, preferably with a plurality of
other parts, to apply a conversion coating at 68.
[0033] Pressure sequence hydro-forming may be used to form a
straight, longitudinally pre-bent and/or transversely pre-formed
tube blank 36. The pre-bent/pre-formed tube 44 is placed in the
hydro-forming die 40 and is filled with the hydro-forming liquid
48, or water, at a low pressure that may be referred to as the
closing pressure before the hydro-forming die 40 is completely
closed. As the hydro-forming die 40 closes, calibration pressure is
gradually increased to shape the tube in the hydro-forming die 40.
The corners of the part are primarily formed during die closing and
the tubular blank retains the nominal wall thickness to enable
forming materials having lower formability and assure maintaining
the structural integrity of the tube 36.
[0034] The internal pressure within the tube resists the tendency
of the tube to collapse that otherwise may occur upon closing the
hydro-forming die 40. The closing fluid pressure in the tube is
always greater than zero. The calibration pressure is used to shape
the tube 36 and allows the use of lower tonnage presses and results
in lower capital costs. In addition, pressure sequence
hydro-forming makes it possible to form complex parts having
greater structural integrity with improved accuracy.
[0035] The pressure sequence hydro-forming process when applied to
an extruded structural tube should be performed to minimize
expansion. Pressure sequence hydro-forming assures the structural
integrity of the part even though the aluminum tubular blank has
lower formability than that of steel.
[0036] While exemplary embodiments are described above, it is not
intended that these embodiments describe all possible forms of the
disclosed apparatus and method. Rather, the words used in the
specification are words of description rather than limitation, and
it is understood that various changes may be made without departing
from the spirit and scope of the disclosure as claimed. The
features of various implementing embodiments may be combined to
form further embodiments of the disclosed concepts.
* * * * *