U.S. patent application number 14/450973 was filed with the patent office on 2016-02-04 for hot-stamping tailor-welded blanks of aluminum sheet.
The applicant listed for this patent is FORD GLOBAL TECHNOLOGIES, LLC. Invention is credited to JO ANN CLARKE, MICHAEL WILLIAM DANYO, NIA R. HARRISON, S. GEORGE LUCKEY, JR..
Application Number | 20160030992 14/450973 |
Document ID | / |
Family ID | 55179071 |
Filed Date | 2016-02-04 |
United States Patent
Application |
20160030992 |
Kind Code |
A1 |
CLARKE; JO ANN ; et
al. |
February 4, 2016 |
HOT-STAMPING TAILOR-WELDED BLANKS OF ALUMINUM SHEET
Abstract
Forming a tailor-welded blank (TWB) having aluminum sheets
includes various elements. For example, a hot-stamping methodology
is applied to a welded blank for meeting load and stiffness
requirements in tandem to weight efficiency. A TWB can result in
improved material utilization, and applying the hot-stamping
methodology can improve the formability of the TWB. After forming
and subsequent processing, a peak-age heat treatment is utilized
such that a lightweight, high strength part may be attained.
Inventors: |
CLARKE; JO ANN; (Plymouth,
MI) ; DANYO; MICHAEL WILLIAM; (Trenton, MI) ;
HARRISON; NIA R.; (Ann Arbor, MI) ; LUCKEY, JR.; S.
GEORGE; (Dearborn, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FORD GLOBAL TECHNOLOGIES, LLC |
Dearborn |
MI |
US |
|
|
Family ID: |
55179071 |
Appl. No.: |
14/450973 |
Filed: |
August 4, 2014 |
Current U.S.
Class: |
148/535 |
Current CPC
Class: |
B21D 35/006 20130101;
B21D 22/022 20130101; C22F 1/04 20130101; C22C 21/06 20130101; C22F
1/05 20130101; C22F 1/002 20130101; C22F 1/047 20130101; C22F 1/057
20130101; C22F 1/053 20130101; C22C 21/10 20130101; B21D 35/005
20130101; C22C 21/02 20130101 |
International
Class: |
B21D 22/02 20060101
B21D022/02; C22F 1/057 20060101 C22F001/057; C22F 1/047 20060101
C22F001/047; C22F 1/05 20060101 C22F001/05; C22F 1/053 20060101
C22F001/053; C22C 21/18 20060101 C22C021/18; C22C 21/06 20060101
C22C021/06; C22C 21/08 20060101 C22C021/08; C22C 21/10 20060101
C22C021/10; C22C 21/14 20060101 C22C021/14; C22C 21/16 20060101
C22C021/16; C22F 1/00 20060101 C22F001/00; C22F 1/04 20060101
C22F001/04 |
Claims
1. A method of forming a tailor-welded blank (TWB) comprising:
fabricating the TWB by welding a first sheet of aluminum to a
second sheet of aluminum; and improving a formability of a weld
created by the welding by: heating the TWB to at least a solidus
temperature of the first sheet; positioning the TWB in a die set;
and closing the die set on the TWB to form the TWB into a part
while simultaneously quenching the part.
2. The method of claim 1, wherein the second sheet includes a
different alloy than the first sheet.
3. The method of claim 2, wherein respective series of the first
sheet and the second sheet are selected from a group consisting of
2xxx, 5xxx, 6xxx, and 7xxx.
4. The method of claim 1, wherein the second sheet includes a
different thickness than the first sheet.
5. The method of claim 4, wherein respective thicknesses of the
first sheet and the second sheet are in a range of about 0.8 mm to
about 4.0 mm.
6. The method of claim 1, wherein fabricating the TWB includes
fabricating a tailor-welded coil and blanking the TWB from the
tailor-welded coil.
7. A method of forming a tailor-welded sheet, which includes a
first sheet of aluminum welded to a second sheet of aluminum, the
method comprising: heating the tailor-welded sheet to at least a
solidus temperature of the first sheet; positioning the
tailor-welded sheet in a die set; and closing the die set on the
tailor-welded sheet to form the tailor-welded sheet into a part
while simultaneously quenching the part, wherein the part includes
a first portion formed by the first sheet and a second portion
formed by the second sheet, and wherein the first portion and the
second portion have different thicknesses.
8. The method of claim 7 further comprising, fabricating a
tailor-welded sheet by welding the first sheet of aluminum to the
second sheet of aluminum.
9. The method of claim 8 further comprising, blanking the
tailor-welded sheet from a tailor-welded coil.
10. The method of claim 7, wherein the first sheet of aluminum
includes a first series of aluminum alloy and the second sheet of
aluminum includes a second series of aluminum alloy, which is
different than the first series.
11. The method of claim 10, wherein the first series is selected
from the group consisting of 2xxx, 5xxx, 6xxx, and 7xxxx series
aluminum alloys, and wherein the second series is also selected
from the group and is different than the first series.
12. The method of claim 7, wherein the first sheet of aluminum
includes a first thickness and the second sheet of aluminum
includes a second thickness, which is different than the first
thickness.
13. The method of claim 7 wherein the step of heating the
tailor-welded sheet is performed outside of the die set, and the
method further comprises the step of transferring the tailor-welded
sheet to the die set after the step of heating the tailor-welded
sheet and before the step of positioning the blank, wherein the
steps of transferring the blank to the die set and positioning the
blank in the die set is performed in about 30 seconds or less.
14. The method of claim 7, wherein quenching the part includes
cooling the part at a quench rate of at least 150.degree.
C./second.
15. The method of claim 7 further comprising, artificially aging
the part to achieve a high strength temper.
16. The method of claim 7 further comprising, aging the part to
achieve a T6 or T7x temper aluminum part.
17. The method of claim 7, wherein the tailor-welded sheet is
positioned in the die set such that the tailor-welded sheet does
not touch the die set.
18. A method of improving room-temperature formability of a weld
that joins a first sheet of aluminum and a second sheet of aluminum
to form a tailor-welded blank (TWB), the method comprising: heating
the TWB to at least a solidus temperature of the first sheet;
positioning the TWB in a die set; and closing the die set on the
TWB to form the tailor-welded sheet into a part while
simultaneously quenching the part.
19. The method of claim 18, wherein respective series of the first
sheet and the second sheet may be different and are selected from
the group consisting of 2xxx, 5xxx, 6xxx, and 7xxx.
20. The method of claim 18, wherein respective thicknesses of the
first sheet and the second sheet are different and are in a range
of about 4.0 mm to about 0.8 mm.
Description
TECHNICAL FIELD
[0001] This application relates to metal forming, and more
specifically to hot stamping tailor-welded blanks.
BACKGROUND
[0002] Automotive structural elements (e.g., panels, rails,
pillars, etc.) are often made from mild steels. These parts
sometimes include multiple regions or portions having different
strength requirements. For instance, in a stamped door inner, a
portion of the door inner that supports hinges might possess higher
strength requirements than other portions of the door inner. As
such, tailor-welded blanks or sheets can be used, which include two
or more sheets of steel having different properties (e.g.,
thickness) that are welded together and that can be conventionally
stamped into a part. Accordingly, the part can be engineered to
meet loading and stiffness requirements with greater weight
efficiency and cost savings.
[0003] In an effort to decrease vehicle weight, aluminum-alloy body
panels have been increasing in popularity, and utilizing
tailor-welded aluminum blanks or sheets might further contribute to
cost and weight savings. However, aluminum welds typically show
reduced strength and formability when stamping compared to parent
material.
SUMMARY
[0004] An embodiment of the present invention is directed to
forming a tailor-welded blank (TWB), which includes a first
aluminum sheet welded to a second aluminum sheet. In one instance,
the TWB is heated to at least a solidus temperature of the first
sheet and is positioned in a die set. The die set is closed on the
TWB to form the TWB into a part while simultaneously quenching the
part.
[0005] Another embodiment includes a method of forming a TWB. The
TWB is fabricated by welding a first sheet of aluminum to a second
sheet of aluminum. The formability of a weld created by the welding
is improved by heating the TWB to at least a solidus temperature of
the first sheet, positioning the TWB in a die set, and closing the
die set on the TWB to form the TWB into a part while simultaneously
quenching the part.
[0006] In an additional embodiment, a method of improving
formability of a weld that joins a first sheet of aluminum and a
second sheet of aluminum includes various elements. For example,
the first and second sheets that are welded together are heated to
a solidus temperature of the first sheet and are positioned in a
die set. The die set is closed on the sheets to form the sheets
into a part while simultaneously quenching the part.
[0007] Embodiments of the invention are defined by the claims
below, not this summary. A high-level overview of various aspects
of the invention is provided here to introduce a selection of
concepts that are further described below in the
detailed-description section. This summary is not intended to
identify key or essential features of the claimed subject matter,
nor is it intended to be used as an aid in isolation to determine
the scope of the claimed subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Illustrative embodiments of the present invention are
described in detail below with reference to the attached drawing
figures, which are incorporated herein by reference, wherein:
[0009] FIG. 1 depicts an exemplary tailor-welded blank in
accordance with an embodiment of the present invention;
[0010] FIG. 2 depicts an exemplary system in accordance with an
embodiment of the present invention;
[0011] FIG. 3 depicts an exemplary staging apparatus in accordance
with an embodiment of the present invention; and
[0012] FIGS. 4 and 5 each depicts a respective flow diagram having
steps that are carried out in accordance with embodiments of the
present invention.
DETAILED DESCRIPTION
[0013] The subject matter of embodiments of the present invention
is described with specificity herein to meet statutory
requirements. But the description itself is not intended to
necessarily limit the scope of claims. Rather, the claimed subject
matter might be embodied in other ways to include different
elements or combinations of elements similar to the ones described
in this document, in conjunction with other present or future
technologies. Terms should not be interpreted as implying any
particular order among or between various steps herein disclosed
except when the order of individual steps is explicitly stated.
[0014] Referring to FIG. 1, a tailor-welded blank (TWB) 12 is
depicted including a first sheet of aluminum 16 and a second sheet
of aluminum 18 that are joined by a weld 17. The TWB 12 might be
created by fusion welding (e.g., laser, arc, etc.) or by friction
stir welding, and typically a butt joint is utilized. For
illustrative purposes, FIG. 1 depicts a weld 17 that joins the
first sheet 16 and the second sheet 18. Although FIG. 1 depicts TWB
12 having only the first sheet 16 and the second sheet, in other
embodiments, the TWB 12 includes more than two different sheets and
includes as many sheets as are desired to form a part.
[0015] The TWB might be used for various purposes, and in one
embodiment, the TWB 12 is stamped into a part for a motor vehicle.
For instance, the TWB might be stamped into a A/B pillar, a rocker,
a roof rail, a cross-car beam, a door inner, and the like. In one
embodiment, it is desirable for the part into which the TWB 12 is
stamped to have portions or regions with different characteristics.
For instance, it might be desirable for a front portion of a door
inner that supports door hinging to be stronger than other regions
of the door inner. As such, in one embodiment, the first sheet 16
and the second sheet 18 are both aluminum and are dissimilar in one
or more respects.
[0016] The first sheet 16 and second sheet 18 might be different in
various respects to optimize the part characteristics. For example,
the first sheet 16 and the second sheet 18 might have different
thicknesses, alloys, or a combination thereof.
[0017] In one embodiment the first sheet 16 includes a first
thickness that is in a range of about 0.8 mm to about 4.0 mm, and
the second sheet 18 includes a second thickness that is different
than the first thickness and is also in the range of about 0.8 mm
to about 4.0 mm.
[0018] In another embodiment, the first sheet 16 and the second
sheet 18 might have different properties (e.g., alloy composition
or series). For instance, in one embodiment, the first sheet 16 and
second sheet 18 are any combination of the alloys 2xxx, 5xxx, 6xxx,
and 7xxxx. That is, aluminum alloys are typically identified by a
four-digit number, the first digit of which generally identifies
the major alloying element. For example, the major alloying element
in 7xxx series aluminum is zinc while the major alloying element of
5xxx series is magnesium and for 6xxx series is magnesium and
silicon. Additional numbers represented by the letter "x" in the
series designation define the exact aluminum alloy. In one
embodiment, a 7075 aluminum alloy may be used that has a
composition of 5.1-6.1% zinc, 2.1-2.9% magnesium, 1.2-2.0% copper,
and less than half a percent of silicon, iron, manganese, titanium,
chromium, and other metals. In addition, the first and second
sheets might have a variety of tempers, such as F, W, O, T4x, T6x,
T7x, and T8x.
[0019] The TWB 12 might be obtained from various sources. For
instance, in one embodiment, the TWB 12 is obtained as a pre-made
blank. Alternatively, a tailor-welded coil might be obtained and
the TWB 12 is cut from the coil. In another embodiment, the TWB 12
is fabricated in a coil and the TWB is blanked from the
tailor-welded coil. For example, a welding apparatus 14 might apply
a weld (e.g., laser, arc, or the like) to two or more sheets of
aluminum to fabricate a tailor-welded coil.
[0020] An embodiment of the present invention is directed to
improving a formability of the weld 17 that joins the first
aluminum sheet 16 and the second aluminum sheet 18. That is, absent
the present invention, the weld 17 includes characteristics that
reduce formability. As such, embodiments hereof address some
manufacturing limitations associated with reduced formability of
welded joints of aluminum-alloy tailor-welded blanks.
[0021] Referring to FIG. 2, a system 10 for forming a tailor-welded
blank 12 (TWB) is shown. The system 10 of FIG. 2 includes a heating
apparatus 20, a transfer apparatus 22, and a die set 24. The
various components of the system 10 function together to fabricate
a tailor-welded blank that is constructed of one or more aluminum
alloys and is formable into a desired part.
[0022] In an embodiment of the present invention, the heating
apparatus 20 heats the TWB 12. The heating apparatus 20 might
includes various types, such as an industrial furnace or oven
capable of producing internal temperatures high enough to heat TWB
12, which are placed in the heating apparatus 20, to a
predetermined temperature. In one embodiment, the heating apparatus
20 heats the TWB 12 to a solution or solidus temperature of at
least one of the first sheet 16 or second sheet 18 of the TWB 12.
In a further embodiment, the heating apparatus 20 does not heat the
TWB 12 past its liquidus (melting) temperature.
[0023] The solution temperature might vary depending on the series
of the first sheet 16 and the second sheet 18. For instance, the
solution temperature for a 7xxx series aluminum alloy is typically
about 460.degree. C. to about 490.degree. C. The solution
temperature is usually the temperature at which a substance is
readily miscible. Miscibility is the property of materials to mix
in all proportions, forming a homogeneous solution. Miscibility may
be possible in all phases; solid, liquid and gas.
[0024] The solidus temperature may be the locus of temperatures on
a curve on a phase diagram below which a given substance is
completely solid. The solidus temperature quantifies the
temperature at which melting of a substance may begin, but not the
temperature at which the substance is melted completely. With some
materials there may be a phase existing between the solidus and
liquidus temperatures wherein the substance consists of solid and
liquid phases simultaneously. The closer the material is to the
solidus temperature, the more the material is in a solid phase, and
the closer the material is to the liquidus temperature, the more
the material is in a liquid phase. As such, the TWB 12 may be
heated to at least the solidus temperature of one of the aluminum
sheets but less than the liquidus temperature, thereby providing a
TWB 12 that is substantially solid to facilitate handling and
transport yet more readily formable due to its near liquid or
partial liquid phase.
[0025] The transfer mechanism 22 is configured to move and position
the TWB 12, which is heated to the solidus temperature of at least
one of the sheets. In at least one embodiment, the transfer
mechanism 22 is a manipulator, such as a robot. The transfer
mechanism 22 might be configured to quickly transfer the TWB 12
from the heating apparatus 20 to the die set 24 to reduce the
opportunity for heat loss from the TWB 12. For example, the system
10 and transfer mechanism 22 may be configured such that the
temperature of the TWB 12 does not decrease to or below the
critical quench temperature of at least one of the aluminum sheets
16 and 18. The critical quench temperature is the temperature at
which quenching must begin to achieve a proper quench of the
material. For example, the critical quench temperature for most
7xxx series aluminum alloys is approximately 415.degree. C.
[0026] The die set 24 is provided to form the TWB 12 into a part
having a predetermined shape. In at least one embodiment, the die
set 24 includes a first die 26, a second die 28, at least one
actuator 30, and a staging apparatus 32.
[0027] The first and/or second dies 26, 28 are configured to form
the TWB 12 into the part having a predetermined shape. An actuator
30 actuates the first die 26 and/or the second die 28 toward or
away from each other and provide force to form the TWB 12. The
actuator 30 may be of any suitable type, such as hydraulic,
pneumatic, mechanical, electromechanical, or combinations thereof.
The die set 24 and actuator 30 combination may also be referred to
as a machine press, stamping press, or quenching press.
[0028] A staging apparatus 32 may be provided for positioning the
TWB 12 between and spaced apart from the first and second dies 26,
28. As such, the staging apparatus 32 may inhibit conductive heat
transfer between the TWB 12 and the die set 24, thereby helping to
maintain the TWB 12 at or above the critical quench temperature.
The staging apparatus 32 may receive the TWB 12 from the transfer
mechanism 22 and may release the TWB 12 as the first die 26 and/or
the second die 28 are closed and engage the TWB 12. In addition,
the system 10 may be configured such that little heat is lost from
the TWB 12 between removal from the heating apparatus 20 and
closing of the die set 24. In at least one embodiment, the
temperature of the TWB 12 may decrease by less than 10.degree. C.;
however, the TWB 12 could experience a greater temperature loss,
such as up to 75.degree. C., such as when the TWB 12 is heated to
490.degree. C. and the critical quench temperature is 415.degree.
C.
[0029] The die set 24 may include piping 34 that facilitates
cooling of the first and/or second dies 26, 28 and quenching of the
part formed from the TWB 12. The piping 34 may be voids or channels
formed into the die set 24, or any combination of externally
connected piping and channels. The piping 34 may be connected to a
cooling source and may receive a heat transfer medium, such as a
fluid, from the cooling source for cooling the die set 24 to a
desired temperature. The heat transfer medium may be any fluid
medium capable of cooling the die set 24 to a predetermined
temperature range, such as from 1.degree. C. to 30.degree. C. The
die set 24 may be cooled in a manner that inhibits formation of
condensation on one or more surfaces of the die set 24. In a mass
production setting, the temperature of the die set 24 may be cooled
to the predetermined temperature range before forming and quenching
a TWB 12 to remove heat that may have been transferred from a TWB
12 to the die set 24 during forming of a previous part.
[0030] In one embodiment, forming the heated TWB 12 into a part
occurs simultaneously with quenching of the part. The quench rate
affects the final temper strength and corrosion performance of the
material. In some embodiments, the quench rate for the aluminum
alloy, as it passes from 400.degree. C. to 290.degree. C., may be
equal to or greater than 150.degree. C./second. The part may be
further cooled to a final temperature from 200.degree. C. to
25.degree. C. before removal of the part from the die set 24 to
provide dimensional stability and facilitate the room temperature
material handling of the part during subsequent processing.
[0031] The system 10 may be designed to operate continuously with a
number of TWB 12 being heated in series or parallel by one or more
heating apparatuses 20 and then transferred to at least one die set
24 for forming and quenching. At least one die set may become
hotter than 30.degree. C. during, or after, the forming of the TWB
12 and/or simultaneous quenching of the part, and as such more than
one die set 24 may be used to provide faster production speeds.
[0032] The part may be removed from the die set 24 by the transfer
mechanism 22, another transferring device, or by hand. The part
then progresses on to subsequent processing which may include
flanging, trimming, and a natural and/or artificial aging to bring
the aluminum alloy part to a high strength temper such as T6 or
T7x.
[0033] Five basic temper designations may be used for aluminum
alloys which are; F--as fabricated, O--annealed, H--strain
hardened, T--thermally treated, and W--as quenched (between
solution heat treatment and artificial or natural aging). The
temper designation may be followed by a single or double digit
number for further delineation. An aluminum alloy with a T6 temper
designation may be an alloy which has been solution heat treated
and artificially aged, but not cold worked after the solution heat
treatment (or such that cold working would not be discernable in
the material properties). T6 may represent the point of peak age
yield strength along the yield strength vs. time and temperature
profile for the material. A T7x temper may designate that a
solution heat treatment has occurred, and that the material was
artificially aged beyond the peak age yield strength (over-aged)
along the yield strength versus time and temperature profile. A T7x
temper material may have a lower yield strength than a T6 temper
material, but this may be done to increase corrosion
performance.
[0034] Referring to FIG. 3, an embodiment of a staging apparatus 32
is shown in more detail. One or more staging apparatuses 32 may be
provided with the die set 24. For example, a staging apparatus 32
may be provided proximate to a corner or side of a die in one or
more embodiments. A staging apparatus 32 may be positioned or
configured so as not to interfere with actuation or closing of the
die set 24. Moreover, the staging apparatus 32 may help insulate or
may be provided with materials that inhibit heat transfer from the
TWB 12 to a die. The staging apparatus 32 may include a base 40, a
support member 42, a finger 44, and an actuator 46.
[0035] The base 40 may be disposed on the die set 24 and may
facilitate mounting of the staging apparatus 32. The support member
42 may extend from and may be fixedly disposed on the base 40. The
support member 42 may include a slot 50. The slot 50 may be
configured to receive and accommodate rotation of the finger
44.
[0036] The finger 44 may be pivotally disposed on the support
member 42. For example, a pivot pin may rotatably couple the finger
44 to the support member 42 in one or more embodiments. The finger
44 may rotate between a first position and a second position. In
the first position, the finger 44 may extend away from the support
member 42 and may support the TWB 12. The finger 44 may rotate with
respect to the support member 42 and toward or into the slot 50 to
a second position (as indicated by the arrows in FIG. 3) to permit
the TWB 12 to disengage the staging apparatus 32 and drop onto a
die, such as the second die 28.
[0037] The actuator 46 may be placed in proximity of the staging
apparatus and may be used to provide position control of finger 44.
For example, in some embodiments the actuator 46 may be an electric
motor connected to the pivot pin which rotates the finger 44 from
the first position to the second position when power is applied,
and a spring 52 may return the finger 44 from the second position
to the first position when power is removed. The actuator 46 may be
controlled by an automated control system, or by an operator. The
actuator 46 may also be a servomechanism utilizing electricity,
hydraulics, pneumatics, magnetic, or mechanical principles, or any
combination, to provide position control of the finger 44.
[0038] Referring to FIG. 4, a flow diagram depicts a series of
steps that, when executed, provide a method 410 of forming a
tailor-welded blank. In describing the steps of FIG. 4, reference
will also be made to FIGS. 2 and 3.
[0039] Step 412 includes fabricating the tailor-welded blank by
welding a first sheet of aluminum to a second sheet of aluminum.
For example, fusion welding or friction stir welding might be used
to join the first sheet 16 to the second sheet 18 with the weld
17.
[0040] The method 410 also includes various steps for improving a
formability of a weld (e.g., weld 17) created by the welding. Step
414 includes heating the tailor-welded blank to at least a solidus
temperature of the first sheet. For instance, the heating apparatus
20 might be used to heat the TWB 12 to the solidus temperature of
at least one of the sheets 16 and 18. At step 416, the TWB is
positioned in the die set. For example, the robot 22 might be used
to move the TWB 12 from the heating apparatus 20 to the dies set
24.
[0041] Step 418 includes closing the die set on the tailor-welded
blank to form the tailor-welded blank into a part while
simultaneously quenching the part. For example, the die set 24 is
closed on the TWB 12 while the cooling coils 34 are used to reduce
a temperature of the part.
[0042] Referring now to FIG. 5, another flow diagram is depicted
showing a series of steps that are similar to method 410, but that
are more detailed. Similar to the method 410, the method 510 is for
processing or forming an aluminum-alloy TWB.
[0043] At 512, the method 510 includes providing an aluminum-alloy
tailor-welded coil. The aluminum-alloy tailor-welded coil might be
fabricated by welding a first sheet to a second sheet, or might be
obtained in a pre-made coil.
[0044] At 514, the coil might be lubricated to facilitate blanking,
if blanking is necessary. For instance, lubrication may aid blank
formation, reduce heat generation at the edges of the blank, and
facilitate blank removal. However, if lubrication is deemed not
necessary, or a pre-made blank is obtained, then step 514 might be
omitted.
[0045] Step 516 includes blanking the coil or otherwise cutting the
coil into pieces to provide smaller workpieces, also referred to
herein as tailor-welded blanks (TWB). The TWB are transferred 518
to a heating apparatus.
[0046] Step 520 includes heating the TWB to a desired temperature,
such as with the heating apparatus 20. The TWB might be heated to
at least either its solution or solidus temperature of one of the
sheets as previously discussed. The step of heating the TWB may
occur between 1 to 45 minutes, and still remain commercially
viable.
[0047] At step 522, a die set 24 is cooled to a predetermined
temperature as previously described. Cooling of the die set may
occur simultaneously with one or more of the previous steps. Step
524 includes transferring the TWB to the die set. For instance, the
TWB 12 may be transferred to the staging apparatus 32 with the
transfer mechanism 22 such that the TWB 12 is spaced apart from the
forming surfaces of the die set 24 as previously discussed. In at
least one embodiment, the transfer mechanism 22 may transfer the
TWB 12 from the heating apparatus 20 to one die set 24 in 30
seconds or less.
[0048] Step 526 includes positioning the TWB 12 in the die set 24,
such as by actuating the staging apparatus 26 from the first
position to the second position to release the TWB 12 onto a die,
such as the second die 28. At step 528, the die set 24 is closed to
form the TWB 12 into a part. In at least one embodiment, the
closing of the die set 24 occurs before the TWB 12 cools past a
critical quench temperature as previously discussed. In at least
one embodiment, the rate of closure of the first and second dies 26
and 28 may be at least 50 millimeters per second to provide "quick
contact" between the surfaces of the TWB 12 and the die set 24 and
allow for effective conductive heat transfer between the TWB 12 and
the die set 24 during quenching.
[0049] Step 530 includes forming and quenching the TWB into a part
having a predetermined shape. Quenching occurs simultaneously with
forming the TWB 12 as previously discussed. Quenching occurs
between a specified temperature cooling range or until the
temperature of the part decreases below a predetermined
temperature. A temperature sensor may be used to detect the
temperature of the part or the die is held for a predetermined
period of time, i.e. the hold time. The predetermined hold time may
be determined by experimentation or by numerical approximation.
[0050] At step 532, the die set 24 is held in a closed position,
and in one embodiment, the die set 24 is held in the closed
position until sufficient heat transfer is complete. In at least
one additional embodiment, the die set 24 remains closed on the
part for approximately 3 to 60 seconds to remove the remaining heat
from the part to be ready for subsequent processing. In addition,
the part may be cooled to a temperature that facilitates material
handling.
[0051] Step 534 includes opening the die set 24 to facilitate
removal of the part, and at step 536, the part is removed from the
die set 24. Manual or automated material handling techniques may be
employed to remove the part as previously discussed. Cooling of the
die set 24 may continue during part removal in one or more
embodiments.
[0052] At step 538, additional manufacturing steps may be performed
on the part. For instance, additional material may be removed from
the part using any suitable process, such as cutting or drilling.
In addition, additional forming steps may be taken, such as bending
or flanging the part to provide a configuration that may not be
provided with the die set 24. Such steps may be performed within a
predetermined period of time, such as within 24 hours, since the
part may become too brittle after that time period to allow for the
additional manufacturing.
[0053] At 540, the part may be aged. Aging of the part may consist
of naturally aging and/or artificially aging to achieve a high
strength temper such as T6 or T7x. There are numerous aging
schedules provided by ASM or MIL standards. One aging schedule that
works with this method is to naturally age the part at room
temperature for 24 hours followed by artificial aging the part at
120.degree. C. for 24 hours.
[0054] The above system and methods may produce a high-strength
aluminum-alloy part that is comprised of sheets having different
characteristics to balance desired strength and energy-absorbing
characteristics with cost and other efficiencies. In addition, the
part can have similar characteristics to that of high strength and
ultra-high strength steels of similar geometry. High strength
aluminum parts may be lighter than parts made from steel of similar
geometry. Furthermore, the system and methods in this application
produce high strength aluminum alloy parts at a high volume, high
quality, and low cost consistent with conventional automotive metal
forming. Thus a part made following the teachings of this
application may replace a steel structural part with an aluminum
alloy structural part without sacrificing safety while reducing
overall vehicle weight. In a vehicular application, a lighter
automotive part, such as a body structure component including but
not limited to a rocker panel, roof rail, bumper structure, or A, B
or C-pillar, may reduce vehicle weight and may result in reduced
fuel consumption and energy conservation.
[0055] Many different arrangements of the various components
depicted, as well as components not shown, are possible without
departing from the scope of the claims below. Embodiments of our
technology have been described with the intent to be illustrative
rather than restrictive. Alternative embodiments will become
apparent to readers of this disclosure after and because of reading
it. Alternative means of implementing the aforementioned can be
completed without departing from the scope of the claims below.
Certain features and subcombinations are of utility and may be
employed without reference to other features and subcombinations
and are contemplated within the scope of the claims.
* * * * *