U.S. patent application number 15/216034 was filed with the patent office on 2018-01-25 for water-based lubrication for hot forming.
The applicant listed for this patent is Ford Global Technologies, LLC. Invention is credited to Nia R. Harrison, S. George Luckey, JR., Mark Edward Nichols, Rosa Lynda Nuno.
Application Number | 20180023173 15/216034 |
Document ID | / |
Family ID | 60889935 |
Filed Date | 2018-01-25 |
United States Patent
Application |
20180023173 |
Kind Code |
A1 |
Nuno; Rosa Lynda ; et
al. |
January 25, 2018 |
Water-Based Lubrication For Hot Forming
Abstract
A manufacturing control system is arranged to cause an aluminum
alloy blank to be heated to at least its solvus temperature, to
cause a die set to be sprayed with a lubricant formulation that
includes water, lubricant, and a surfactant, to cause the blank to
be positioned in the die set while heated such that the blank does
not touch the die set, and to cause the die set to close on the
blank to form the blank into a part while quenching the part.
Inventors: |
Nuno; Rosa Lynda; (Jerome,
MI) ; Harrison; Nia R.; (Ann Arbor, MI) ;
Nichols; Mark Edward; (Saline, MI) ; Luckey, JR.; S.
George; (Dearborn, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies, LLC |
Dearborn |
MI |
US |
|
|
Family ID: |
60889935 |
Appl. No.: |
15/216034 |
Filed: |
July 21, 2016 |
Current U.S.
Class: |
148/691 |
Current CPC
Class: |
C21D 1/60 20130101; C22F
1/04 20130101; B21D 22/022 20130101; C21D 1/667 20130101; B21D
22/201 20130101 |
International
Class: |
C22F 1/04 20060101
C22F001/04; C21D 1/667 20060101 C21D001/667; B21D 22/02 20060101
B21D022/02; C21D 1/60 20060101 C21D001/60 |
Claims
1. A method comprising: heating an aluminum alloy blank to at least
its solvus temperature; spraying portions of a die set with a
lubricant formulation that includes water, lubricant and a
surfactant; positioning the blank in the die set while heated such
that the blank does not touch the die set; and closing the die set
on the blank to form the blank into a part while quenching the
part.
2. The method of claim 1, wherein the surfactant includes
acetylenic diol.
3. The method of claim 1, wherein the surfactant includes alcohol
ethoxylate.
4. The method of claim 1, wherein the lubricant formulation by
volume includes more water than lubricant and surfactant.
5. The method of claim 1, wherein the lubricant formulation by
volume includes less than 5% surfactant.
6. The method of claim 1, wherein the aluminum alloy blank is an
F-temper aluminum alloy blank.
7. The method of claim 6, wherein the aluminum alloy blank is an
F-temper 6xxx aluminum alloy blank.
8. The method of claim 6, wherein the aluminum alloy blank is an
F-temper 7xxx aluminum alloy blank.
9. The method of claim 1 further comprising cooling the die set to
a temperature between 1.degree. C. to 30.degree. C.
10. The method of claim 1, wherein the solvus temperature is at
least 450.degree. C.
11. The method of claim 1, wherein the spraying includes spraying
the portions with a first lubricant formulation and spraying other
portions of the die set with a second lubricant formulation
different than the first to obtain different formability and quench
efficiency performance between the portions and other portions
during the closing.
12. A manufacturing system comprising: a furnace or oven configured
to heat an aluminum alloy blank to at least its solvus temperature;
a die set; a nozzle arrangement configured to spray portions of the
die set with a lubricant formulation that includes water, lubricant
and a surfactant; a transfer mechanism configured to position the
blank in the die set while heated such that the blank does not
touch the die set; and an actuator configured to close the die set
on the blank to form the blank into a part while quenching the
part.
13. The system of claim 12, wherein the surfactant includes
acetylenic diol.
14. The system of claim 12, wherein the surfactant includes alcohol
ethoxylate.
15. The system of claim 12, wherein the lubricant formulation by
volume includes more water than lubricant and surfactant.
16. The system of claim 12, wherein the lubricant formulation by
volume includes less than 5% surfactant.
17. The system of claim 12, wherein the aluminum alloy blank is an
F-temper aluminum alloy blank.
18. The system of claim 17, wherein the aluminum alloy blank is an
F-temper 6xxx aluminum alloy blank.
19. The system of claim 17, wherein the aluminum alloy blank is an
F-temper 7xxx aluminum alloy blank.
20. The system of claim 12 further comprising piping configured to
cool the die set to a temperature between 1.degree. C. to
30.degree. C.
21. The system of claim 12, wherein the solvus temperature is at
least 450.degree. C.
22. The system of claim 12, wherein the nozzle arrangement is
further configured to spray other portions of the die set with
another lubricant formulation to obtain different formability and
quench efficiency performance between the portions and other
portions to obtain different formability and quench efficiency
performance between the portions and other portions.
23. A manufacturing control system comprising: one or more
controllers configured to heat an aluminum alloy blank via a heater
to at least its solvus temperature, to spray portions of a die set
via a nozzle with a lubricant formulation that includes water,
lubricant, and a surfactant, to position the blank in the die set
while heated via a transfer mechanism such that the blank does not
touch the die set, and to close the die set on the blank via an
actuator to form the blank into a part while quenching the
part.
24. The system of claim 23, wherein the surfactant includes
acetylenic diol.
25. The system of claim 23, wherein the surfactant includes alcohol
ethoxylate.
26. The system of claim 23, wherein the lubricant formulation by
volume includes more water than lubricant and surfactant.
27. The system of claim 23, wherein the lubricant formulation by
volume includes less than 5% surfactant.
28. The system of claim 23, wherein the aluminum alloy blank is an
F-temper aluminum alloy blank.
29. The system of claim 28, wherein the aluminum alloy blank is an
F-temper 6xxx aluminum alloy blank.
30. The system of claim 28, wherein the aluminum alloy blank is an
F-temper 7xxx aluminum alloy blank.
31. The system of claim 23, wherein the one or more controllers are
further configured to cool the die set via piping to a temperature
between 1.degree. C. to 30.degree. C.
32. The system of claim 23, wherein the solvus temperature is at
least 450.degree. C.
33. The system of claim 23, wherein the one or more controllers are
further configured to spray other portions of the die set via a
nozzle with another lubricant formulation to obtain different
formability and quench efficiency performance between the portions
and other portions.
Description
TECHNICAL FIELD
[0001] This disclosure relates to hot forming of aluminum alloy
parts and lubricant formulations used therefor.
BACKGROUND
[0002] Automotive body panels have long been made from mild steels.
Aluminum alloy body panels, however, have been increasing in
popularity given their light weight. 5xxx and 6xxx series aluminum
alloys, which are aluminum-magnesium and aluminum-magnesium-silicon
alloys, have been of interest in this regard as they may be shaped
and processed by methods consistent with those of mild steel.
[0003] Aluminum-zinc alloys of the 7xxx series at T6 or T7x tempers
have strengths similar to those of high and ultra-high strength
steels and can achieve yield strengths exceeding 400 MPa. T6 and
T7x temper aluminum-zinc alloys, however, cannot be conventionally
stamped as these alloys have little to no formability at room
temperature.
SUMMARY
[0004] In one embodiment, a method includes heating an aluminum
alloy blank to at least its solvus temperature, spraying portions
of a die set with a lubricant formulation that includes water,
lubricant and a surfactant, positioning the blank in the die set
while heated such that the blank does not touch the die set, and
closing the die set on the blank to form the blank into a part
while quenching the part.
[0005] In another embodiment, a manufacturing system includes a
furnace or oven configured to heat an aluminum alloy blank to at
least its solvus temperature, a die set, and a nozzle arrangement
configured to spray portions of the die set with a lubricant
formulation that includes water, lubricant and a surfactant. The
system also includes a transfer mechanism configured to position
the blank in the die set while heated such that the blank does not
touch the die set, and an actuator configured to close the die set
on the blank to form the blank into a part while quenching the
part.
[0006] In yet another embodiment, a manufacturing control system
includes one or more controllers. The one or more controllers are
configured to heat an aluminum alloy blank via a heater to at least
its solvus temperature, to spray portions of a die set via a nozzle
with a lubricant formulation that includes water, lubricant, and a
surfactant, to position the blank in the die set while heated via a
transfer mechanism such that the blank does not touch the die set,
and to close the die set on the blank via an actuator to form the
blank into a part while quenching the part
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a perspective view of a hot forming station.
[0008] FIG. 2 is a block diagram of the hot forming station of FIG.
1.
[0009] FIG. 3 is a flow chart of an algorithm for hot forming an
aluminum alloy blank.
DETAILED DESCRIPTION
[0010] Embodiments of the present disclosure are described herein.
It is to be understood, however, that the disclosed embodiments are
merely examples and other embodiments can take various and
alternative forms. The figures are not necessarily to scale; some
features could be exaggerated or minimized to show details of
particular components. Therefore, specific structural and
functional details disclosed herein are not to be interpreted as
limiting, but merely as a representative basis for teaching one
skilled in the art to variously employ the embodiments.
[0011] As those of ordinary skill in the art will understand,
various features illustrated and described with reference to any
one of the figures can be combined with features illustrated in one
or more other figures to produce embodiments that are not
explicitly illustrated or described. The combinations of features
illustrated provide representative embodiments for typical
applications. Various combinations and modifications of the
features consistent with the teachings of this disclosure, however,
could be desired for particular applications or
implementations.
[0012] So called "hot forming" has been used to shape, for example,
F-temper 6xxx or 7xxx series aluminum alloy blanks into automotive
components. In one example, an F-temper 7xxx series aluminum blank
is heated to at least its solvus temperature and then positioned in
a die set so as to not touch the die set. The die set is then
closed to form the blank while also quenching it.
[0013] Lubricants are often used in sheet forming applications.
They can reduce friction between blank and die, which allows for
smooth and controlled metal flow. And, they can assist with part
removal, remove undesired heat, and extend die life. Lubricant
choice and application within the context of hot forming aluminum
alloy operations, however, can be more complicated as compared with
warm forming aluminum alloy operations due to the high blank
temperatures achieved prior to hot forming. (These temperatures can
exceed 250.degree. C.--a temperature at which certain lubricants
may no longer function.) Here, lubricants of particular formulation
are applied to dies of hot forming stations as explained in more
detail below.
[0014] With reference to FIG. 1, a manufacturing system 10 for
forming a blank 12 includes a heating apparatus 14, a transfer
mechanism 16, and a die set 18. In one example, the blank 12 is an
F-temper 7xxx series aluminum alloy blank. Other alloys, however,
are also contemplated. The heating apparatus 14, as the name
suggests, heats the blank 12, and may be an industrial furnace or
oven capable of producing internal temperatures high enough to the
heat blanks 12 placed therein to a predetermined temperature, such
as a solution temperature of the blanks 12. In certain
circumstances, however, the heating apparatus 14 may not heat the
blanks 12 past their liquidus (melting) temperature.
[0015] The solution temperature for a 7xxx series aluminum alloy
may be approximately 450.degree. C. to 490.degree. C. The solution
temperature (or solid solution temperature) is the temperature at
which a substance is readily miscible, which is the property of
materials to mix in all proportions forming a homogeneous
solution.
[0016] The solidus temperature is the collection of temperatures 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 existence between the solidus and liquidus temperatures such
that the substance consists of solid and liquid phases
simultaneously. The closer the material temperature is to the
solidus temperature, the more the material is in a solid phase. The
closer the material temperature is to the liquidus temperature, the
more the material is in a liquid phase. As such, the blank 12 may
be heated to at least its solvus temperature but less than its
solidus temperature to provide a blank that is substantially solid
to facilitate handling and transport yet more readily formable The
solvus temperature indicates the limits of solubility of hardening
alloy elements into the aluminum matrix. Above the solvus
temperature, for a given alloy, is the solid solution temperature
range.
[0017] The transfer mechanism 16 may be configured to move and
position the blank 12. The transfer mechanism 16, in some examples,
may be a manipulator such as a robot, an arm, or conveyor
arrangement. The transfer mechanism 16 may be configured to quickly
transfer the blank 12 from the heating apparatus 14 to the die set
18 to reduce the opportunity for heat loss from the blank 12. For
example, the system 10 and transfer mechanism 16 may be configured
such that the temperature of the blank 12 does not decrease to or
below its critical quench temperature--the temperature at which
quenching must begin to achieve a proper quench of the material.
The critical quench temperature for most 7xxx series aluminum
alloys, for example, is approximately 400.degree. C.
[0018] The die set 18 is provided to form the blank 12 into a part
having a predetermined shape. The die set 18, in some examples,
includes a first die 20, a second die 22, at least one actuator 24,
and a staging apparatus 26. The first and/or second dies 20, 22 are
configured to form the blank 12 into the predetermined shape. The
actuator 24 actuates the first die 20 and/or the second die 22
toward or away from each other and provides force to form the blank
12. The actuator 24 may be of any suitable type, such as hydraulic,
pneumatic, mechanical, electromechanical, or combinations thereof.
The die set 18 and actuator 24 collectively may also be referred to
as a machine press, stamping press, or quenching press.
[0019] The staging apparatus 26 may be provided for positioning the
blank 12 between and spaced apart from the first and second dies
20, 22. As such, the staging apparatus 26 may inhibit conductive
heat transfer between the blank 12 and the die set 18, thereby
helping to maintain the blank 12 at or above its critical quench
temperature. The staging apparatus 26 may receive the blank 12 from
the transfer mechanism 16 and may release the blank 12 as the first
die 20 and/or the second die 22 are closed and engage the blank 12.
In addition, the system 10 may be configured such that little heat
is lost from the blank 12 between removal from the heating
apparatus 14 and closing of the die set 18. In one example, the
temperature of the blank 12 may decrease by less than 10.degree. C.
The blank 12, however, could experience a greater temperature loss,
such as up to a 90.degree. C. assuming that the blank 12 is heated
to 490.degree. C. and the critical quench temperature is
400.degree. C.
[0020] The die set 18 may include piping 28 that facilitates
cooling of the first and/or second dies 20, 22 and quenching of the
part formed from the blank 12. The piping 28 may be voids or
channels formed into the die set 18, or any combination of
externally connected piping and channels. The piping 28 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 18 to a desired temperature (e.g., 1.degree. C. to
30.degree. C.). The die set 18 may be cooled in a manner that
inhibits formation of condensation on one or more surfaces thereon.
In a mass production setting, the temperature of the die set 18 may
be cooled to the predetermined temperature range before forming and
quenching a blank to remove heat that may have been transferred
from a previous blank to the die set 18.
[0021] Forming the heated blank 12 into a part may occur
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 an aluminum
alloy, as it transitions for example from 400.degree. C. to
290.degree. C., may be equal to or greater than 150.degree. C. per
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 18 to provide dimensional stability during subsequent
processing.
[0022] The system 10 may be designed to operate continuously with a
number of blanks being heated in series or parallel by one or more
heating apparatuses and then transferred to at least one die set
for forming and quenching. At least one of the die sets may become
hotter than 30.degree. C. during, or after, blank forming.
[0023] The part may be removed from the die set 18 by the transfer
mechanism 16, another transferring device, or by hand. The part
then proceeds on to subsequent processing which may include
flanging, trimming, and natural and/or artificial aging to bring
the aluminum alloy part to a high strength temper such as T6 or
T7x.
[0024] To improve the quench and metal flow behavior during
forming, a water-based lubricant is applied (e.g., sprayed) onto
the dies 20, 22 prior to closing of the die set 18 around the blank
12 (e.g., prior to the transfer mechanism positioning the blank
between the dies 20, 22). Because most production die sets, such as
the die set 18, can have miscellaneous oils and grease thereon from
maintenance activities and anti-corrosion treatments, a surfactant
is added to the lubricant formulation to maintain the local
as-applied coating weight prior to hot stamping.
[0025] Because the lubricant formulation is water based, it does
not build up on the surface of the dies 20, 22 to the same extent
as non-water based formulations: the die faces remain relatively
clean and do not require frequent cleaning. Other benefits include
that (i) the dies 20, 22 may be cleaned with hot (e.g., 60.degree.
C.) water without a degreaser, (ii) the water may contain an
alkaline or acid concentrate to support proper surface preparation
for subsequent pretreatment or paint processes, (iii) no
solvent-based VOC or smoke will be produced during the quenching
process, (iv) the coating weight and lubricant concentration may be
varied on different areas of the dies 20, 22 via spot application
to support formability and quench efficiency, and (v) the process
window and robustness may be increased via more uniform quench
rates and larger die face overcuts.
[0026] In one example, the lubricant is a die lubricant normally
used in forging applications (e.g., FORGE EASE AL 278). It was
initially discovered that this lubricant performed well when
diluted with isopropyl alcohol (IPA) with a concentration of 1:3
(lubricant:IPA) and applied to aluminum alloy blanks prior to warm
forming. As such, this formulation was attempted within the context
of hot forming. The lubricant formulation, however, was applied to
the die set as opposed to the blanks because of the high blank
temperatures associated with hot forming. Although favorable
results were achieved, it was noted that IPA can be flammable. An
alternative to IPA was thus sought.
[0027] A surfactant that is a combination of an acetylenic diol and
an alcohol ethoxylate (e.g., DYNOL 800) was found to be a suitable
replacement for IPA. That is, non-ionic surfactants are expected to
be preferable to anionic or cationic surfactants. In one example, a
ratio of water to lubricant to surfactant of 90% water, 10%
lubricant and adding 3% surfactant was found to be effective. For
example if the water/lubricant mixture is to be 3000 mL, then the
amount of water would be 2700 mL, the amount of lubricant would be
300 mL, and the amount of surfactant would be 93 mL.
[0028] This lubricant formulation was able to be uniformly applied
with no streaks or heavy film residue. Because the formulation is
primarily water, the quench efficiency associated with the hot
forming process is improved.
[0029] With reference to FIG. 2, the system 10 is shown to include
one or more controllers 30 in communication with and operatively
arranged to control the heating apparatus 14, transfer mechanism
16, actuator 24, and a spray nozzle arrangement 32. The controllers
30 may be a distributed set of processors or a single processor,
etc. With further reference to FIG. 3, the controllers 30 at
operation 34 may command the heating apparatus 14 to heat an
aluminum alloy blank to at least its solvus temperature. At
operation 36, the controllers 30 may command the spray nozzle
arrangement 32 to spray the dies 20, 22 with a lubricant
formulation such as those contemplated herein. As mentioned above,
the concentration of lubricant can be varied to achieve different
formability and quench efficiency objectives. For example, a
lubricant formulation having relatively more lubricant can be
initially applied by the spray nozzle arrangement 32 to certain
portions of the dies 20, 22 while another lubricant formulation
having relatively less lubricant can be subsequently applied by the
spray nozzle arrangement 32 (or another spray nozzle arrangement)
to other portions of the dies 20, 22. At operation 38, the
controllers 30 may command the transfer mechanism 16 to position
the blank while heated within the dies 20, 22 so that the blank
does not come into contact with the dies 20, 22. And, the
controllers 30 at operation 40 may command the actuator 24 to close
the dies 20, 22 to form a part while quenching the part.
[0030] The processes, methods, logic, or strategies disclosed may
be deliverable to and/or implemented by a processing device,
controller, or computer, which may include any existing
programmable electronic control unit or dedicated electronic
control unit. Similarly, the processes, methods, logic, or
strategies may be stored as data and instructions executable by a
controller or computer in many forms including, but not limited to,
information permanently stored on various types of articles of
manufacture that may include persistent non-writable storage media
such as ROM devices, as well as information alterably stored on
writeable storage media such as floppy disks, magnetic tapes, CDs,
RAM devices, and other magnetic and optical media. The processes,
methods, logic, or strategies may also be implemented in a software
executable object. Alternatively, they may be embodied in whole or
in part using suitable hardware components, such as Application
Specific Integrated Circuits (ASICs), Field-Programmable Gate
Arrays (FPGAs), state machines, controllers or other hardware
components or devices, or a combination of hardware, software and
firmware components.
[0031] 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 previously described, the features of various
embodiments may be combined to form further embodiments of the
invention that may not be explicitly described or illustrated.
While various embodiments could have been described as providing
advantages or being preferred over other embodiments or prior art
implementations with respect to one or more desired
characteristics, those of ordinary skill in the art recognize that
one or more features or characteristics may be compromised to
achieve desired overall system attributes, which depend on the
specific application and implementation. These attributes may
include, but are not limited to cost, strength, durability, life
cycle cost, marketability, appearance, packaging, size,
serviceability, weight, manufacturability, ease of assembly, etc.
As such, embodiments described as less desirable than other
embodiments or prior art implementations with respect to one or
more characteristics are not outside the scope of the disclosure
and may be desirable for particular applications.
* * * * *