U.S. patent application number 11/536048 was filed with the patent office on 2008-04-03 for lubricant formulation for high temperature metal forming processes.
This patent application is currently assigned to GM GLOBAL TECHNOLOGY OPERATIONS, INC.. Invention is credited to Michael D. Hanna, Paul E. Krajewski, James G. Schroth.
Application Number | 20080078225 11/536048 |
Document ID | / |
Family ID | 39259834 |
Filed Date | 2008-04-03 |
United States Patent
Application |
20080078225 |
Kind Code |
A1 |
Hanna; Michael D. ; et
al. |
April 3, 2008 |
Lubricant formulation for high temperature metal forming
processes
Abstract
Improved lubricant system useful in metal forming processes. The
lubricant formulations contain boron nitride lubricant with
graphite additions. These formulations enhance lubricity while
maintaining good adherence at elevated temperatures.
Inventors: |
Hanna; Michael D.; (West
Bloomfield, MI) ; Krajewski; Paul E.; (Sterling
Heights, MI) ; Schroth; James G.; (Troy, MI) |
Correspondence
Address: |
GENERAL MOTORS CORPORATION;LEGAL STAFF
MAIL CODE 482-C23-B21, P O BOX 300
DETROIT
MI
48265-3000
US
|
Assignee: |
GM GLOBAL TECHNOLOGY OPERATIONS,
INC.
Detroit
MI
|
Family ID: |
39259834 |
Appl. No.: |
11/536048 |
Filed: |
September 28, 2006 |
Current U.S.
Class: |
72/42 |
Current CPC
Class: |
B21D 37/18 20130101 |
Class at
Publication: |
72/42 |
International
Class: |
B21D 37/18 20060101
B21D037/18 |
Claims
1. An elevated temperature metal forming process comprising the
steps of: heating a metal work piece to a temperature of at least
250 degrees C.; applying a lubricant formulation to at least one of
(a) a metal work piece surface and (b) a surface of a formation
tool; deforming the metal work piece within the formation tool to
substantially conform with the surface of the formation tool; and
removing the metal work piece from the formation tool, wherein the
lubricant formulation comprises boron nitride in combination with
not less than about 5% graphite.
2. The invention according to claim 1 wherein said metal forming
process is quick plastic forming.
3. The invention according to claim 1 wherein said metal forming
process is superplastic forming.
4. The invention according to claim 1 wherein said metal forming
process is warm forming using complementary male and female
formation tools.
5. The invention according to claim 1 wherein said metal forming
process is an aluminum forming process.
6. The invention according to claim 1 wherein said metal forming
process is a magnesium forming process.
7. An elevated temperature metal forming process comprising the
steps of: heating a metal work piece to a temperature of at least
250 degrees C.; applying a lubricant formulation to at least one of
(a) a metal work piece surface and (b) a surface of a formation
tool; deforming the metal work piece within the formation tool to
substantially conform with the surface of the formation tool; and
removing the metal work piece from the formation tool, wherein the
lubricant formulation consists essentially of boron nitride in
combination with about 10% to about 50% graphite.
8. The invention according to claim 7, wherein said metal forming
process is quick plastic forming.
9. The invention according to claim 7, wherein said metal forming
process is superplastic forming.
10. The invention according to claim 7 wherein said metal forming
process is warm forming using complementary male and female
formation tools.
11. The invention according to claim 7 wherein said metal forming
process is an aluminum forming process.
12. The invention according to claim 7 wherein said metal forming
process is a magnesium forming process.
13. An elevated temperature metal forming process comprising the
steps of: heating a metal work piece to a temperature of at least
250 degrees C.; applying a lubricant formulation to at least one of
(a) a metal work piece surface and (b) a surface of a formation
tool; deforming the metal work piece within the formation tool to
substantially conform with the surface of the formation tool; and
removing the metal work piece from the formation tool, wherein the
lubricant formulation consists essentially of boron nitride in
combination with about 5% to about 33% graphite.
14. The invention according to claim 13, wherein said metal forming
process is quick plastic forming.
15. The invention according to claim 13, wherein said metal forming
process is superplastic forming.
16. The invention according to claim 13 wherein said metal forming
process is warm forming using complementary male and female
formation tools.
17. The invention according to claim 13 wherein said metal forming
process is an aluminum forming process.
18. The invention according to claim 13, wherein said metal forming
process is a magnesium forming process.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to lubricant
formulations useful for elevated temperature metal forming
processes such as quick plastic forming, superplastic forming, and
warm forming processes.
BACKGROUND OF THE INVENTION
[0002] Development of lubricants for elevated temperature metal
forming processes such as quick plastic forming (QPF), superplastic
forming (SPF), or warm forming requires the following features: low
coefficient of friction, good adhesion to the blank, uniform
application pattern, low cost and ease of removal after forming.
Petrochemical based lubricants are ineffective due to the high
temperatures utilized in these processes. The most commonly used
lubricant for processes involving such elevated temperatures is
boron nitride (BN). However, other lubricants such as graphite,
molybdenum disulfide, and magnesium hydroxide (commonly referred to
as milk of magnesia when in aqueous suspension) have been used.
SUMMARY OF THE INVENTION
[0003] This invention is believed to provide advantages and
alternatives over prior practices by providing improved lubricant
formulations useful in elevated high temperature metal forming
processes. The formulations contain boron nitride lubricant with
graphite additions. These formulations enhance lubricity while
maintaining good adherence to the surface of the blank.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The accompanying drawings which are incorporated in and
which constitute a portion of this specification illustrate an
exemplary embodiment of the invention which, together with the
general description above and the detailed description set forth
below will serve to explain the principles of the invention
wherein;
[0005] FIG. 1 illustrates a cross sectional view of a metal blank
and female and male shaping tools prior to metal forming;
[0006] FIG. 2 illustrates a cross sectional view of a metal blank
and female and male shaping tools during metal forming;
[0007] FIG. 3 illustrates a cross sectional view of a metal blank
and female and male shaping tools upon completion of metal
forming;
[0008] FIG. 4 illustrates a cross sectional view of a metal blank
and female and male shaping tools after removal of the male
tool;
[0009] FIG. 5 illustrates a cross section view of a metal blank and
female and male shaping tools after removal of the formed metal
blank; and
[0010] FIG. 6 illustrates the effect of graphite to boron nitride
ratio on coefficient of friction.
[0011] While embodiments of the invention have been illustrated and
generally described above and will hereinafter be described in
connection with certain potentially preferred procedures and
practices, it is to be understood and appreciated that in no event
is the invention to be limited to such embodiments and procedures
as may be illustrated and described herein. On the contrary, it is
intended that the present invention shall extend to all
alternatives and modifications as may embrace the broad principles
of the invention within the true spirit and scope thereof.
DETAILED DESCRIPTION
[0012] For ease of reference and understanding, the following
description is set forth with respect to a simplified exemplary
metal formation process. Importantly, it is to be understood that
the lubrication system of the present invention is in no way
limited to such a formation process. Rather, it is contemplated and
intended that the lubrication system will be broadly applicable to
any number of elevated temperature metal formation practices.
[0013] Reference will now be made to the various drawings wherein
to the extent possible, like elements are designated by
corresponding reference numerals in the various views. FIGS. 1-5
illustrate schematically a simplified exemplary so called "warm
forming" practice utilizing male and female formation tool members.
In the illustrated practice a female member 12 includes a mold
cavity 32, bottom surface 14, and two opposing wall surfaces 16. A
metal blank 22 is placed on top of the female member such that a
portion of the bottom surface 30 of the metal blank 22 is in direct
contact with the outer surface 24 of the female member 12.
[0014] FIG. 1 shows the metal blank 22 in position between female
member 12 and a complementary male tool 18 such that the upper
surface 28 of the metal blank 22 faces the male tool 18. Means (not
shown) can be provided to heat both the male tool 18 and the metal
blank 22 to a suitable temperature. The male tool 18 is pressed
against the upper surface 28 of the metal blank 22. This operation
results in creation of an interface region 40 (FIG. 2) between the
male tool 18 and the upper surface 28 of the metal blank 22 and
causes deformation of the metal blank 22 to conform to the shape of
the mold cavity 32 of the female member 12.
[0015] As shown in FIG. 2, the pressure of the male tool 18 acting
on the upper surface 28 of the metal blank 22 deforms the metal
blank downwardly toward the bottom surface 14 of the female member
12. The bottom surface 30 of the metal blank 22 engages a portion
of the opposing wall surfaces 16 creating an interface region 38
between the female member 12 and the bottom surface 30 of the metal
blank 22. In FIG. 3, the male tool 18 has pressed the bottom
surface 30 of the metal blank completely against the opposing walls
16 and the bottom 14 of the female member 12. This further
deformation creates a continuous interface region 38 between the
female member 12 and the metal blank 22 and a continuous interface
region 40 between the male tool 18 and the metal blank. At the
completion of the forming operation, the male tool 18 is lifted
from engagement with the upper surface 28 of the metal blank 22
(FIG. 4) and the metal blank 22 is removed from the female member
12 (FIG. 5).
[0016] As will be appreciated by those of skill in the art, the
formation process illustrated and described in FIGS. 1-5 is
exemplary only. Any number of other elevated temperature formation
processes may also be utilized. By way of example only, and not
limitation, various elevated temperature forming processes are
disclosed in U.S. Pat. No. 5,819,572 to Krajewski, the contents of
which are incorporated herein by reference in their entirety.
[0017] Regardless of the formation practice utilized, some type of
lubrication is typically used during metal forming processes.
Lubrication is needed to avoid sticking and thereby facilitate
deformation of the work piece. Lubrication also serves to assist in
the release of the formed part from die and tool members. The
lubricant may be applied to the surface of the work piece
undergoing deformation and/or to surfaces of the formation
tools.
[0018] The instant invention provides an improved lubrication
system utilizing boron nitride (BN) lubricant with graphite
additions to enhance lubricity while maintaining good adherence to
the metal blank and/or tool members to which it is applied. In one
potentially preferred embodiment, addition of at least 5% and more
preferably about 5% to about 50% graphite to boron nitride results
in improved lubricity (lower coefficient of friction) compared to
BN alone. Unlike lubrication formulations which are predominantly
graphite, the inventive boron nitride-graphite formulations
maintain good adhesion to the metal blank and formation tool
surfaces. Other constituents may be present in the lubricant
provided they do not materially degrade the features of lubricity
and adhesion.
[0019] According to the contemplated practice, the inventive boron
nitride-graphite formulations can be sprayed on the metal blank or
other work piece using conventional paint spraying techniques and
can be removed with standard techniques currently used for pure BN.
In a potentially preferred practice, the metal work piece is
aluminum or magnesium although other work piece materials may
likewise be used. The inventive boron nitride-graphite formulations
are believed to be particularly suitable for formation practices
carried out at temperatures of about 250 degrees C. or greater.
[0020] The substantial benefits in lubricity achieved as a result
of graphite addition are illustrated in FIG. 6. In this chart
coefficient of friction (CoF) is measured for different levels of
graphite addition to boron nitride. Coefficient of friction was
measured using a Cameron Plint reciprocating plate on plate test
procedure at 450 degrees C. The test was duplicated at each level
of graphite addition to confirm relative performance.
[0021] As shown, standard boron nitride lubricant with no graphite
addition (far left columns) yielded substantially greater
coefficient of friction levels than samples with graphite addition.
The data also show that with the addition of graphite lubricity
tends to be maintained at substantially equivalent levels for
longer time periods. This is reflected by the fact that there was
no substantial increase in coefficient of friction during latter
stages of the friction test. Moreover, a visual examination of
samples following the friction tests showed that pure graphite (far
right columns) tended to delaminate to some degree while the BN
graphite combinations maintained substantial adherence. The
lubricant blend thus provides the benefit of improved lubricity in
combination with long term adhesion under friction.
[0022] It is to be understood that while the present invention has
been illustrated and described in relation to potentially preferred
embodiments, constructions, and procedures, that such embodiments,
constructions, and procedures are illustrative only and that the
invention is in no event limited thereto. Rather, it is
contemplated that modifications and variations embodying the
principals of the invention will no doubt occur to those of skill
in the art. It is therefore contemplated and intended that the
present invention shall extend to all such modifications and
variations as may incorporate the broad aspects of the invention
within the true spirit and scope thereof.
* * * * *