U.S. patent application number 13/892028 was filed with the patent office on 2013-10-17 for apparatus and method for imparting selected topographies to aluminum sheet metal.
The applicant listed for this patent is ALCOA, INC. Invention is credited to David E. Coleman, June M. Epp, Tom J. Kasun, Salvador A. Marcilla Gomis, Norman J. Panseri, Shen Sheu, Patricia A. Stewart, Neville C. Whittle, Julie A. Wise.
Application Number | 20130273394 13/892028 |
Document ID | / |
Family ID | 49325384 |
Filed Date | 2013-10-17 |
United States Patent
Application |
20130273394 |
Kind Code |
A1 |
Sheu; Shen ; et al. |
October 17, 2013 |
Apparatus and Method for Imparting Selected Topographies to
Aluminum Sheet Metal
Abstract
A method for surface treating work rolls to produce isotropic
textured aluminum sheet features indenting the surface of the
working rolls that produce the sheet with spherical media such as
steel ball bearings having the requisite properties to avoid
fracture and resulting in a smooth surface lacking facets. The
spherical media can be introduced into a nip between two rolls and
indent by compression, but ultrasonic peening or knurling. The
aluminum sheet produced by the roll has properties that facilitate
mechanical forming, such as when the sheet is processed by forming
tools.
Inventors: |
Sheu; Shen; (Murrysville,
PA) ; Wise; Julie A.; (Natrona Heights, PA) ;
Kasun; Tom J.; (Export, PA) ; Whittle; Neville
C.; (Irwin, PA) ; Epp; June M.; (Pittsburgh,
PA) ; Coleman; David E.; (Murrysville, PA) ;
Panseri; Norman J.; (Irvin, PA) ; Marcilla Gomis;
Salvador A.; (Alicante, ES) ; Stewart; Patricia
A.; (Pittsburgh, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ALCOA, INC |
Pittsburgh |
PA |
US |
|
|
Family ID: |
49325384 |
Appl. No.: |
13/892028 |
Filed: |
May 10, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13673468 |
Nov 9, 2012 |
|
|
|
13892028 |
|
|
|
|
61558504 |
Nov 11, 2011 |
|
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Current U.S.
Class: |
428/687 ; 29/428;
72/199; 72/252.5; 72/53 |
Current CPC
Class: |
B21B 28/02 20130101;
B24C 1/10 20130101; B24C 1/06 20130101; B21B 27/005 20130101; B21B
1/227 20130101; B21B 2003/001 20130101; Y10T 29/49826 20150115;
Y10T 428/12993 20150115 |
Class at
Publication: |
428/687 ; 72/53;
72/252.5; 29/428; 72/199 |
International
Class: |
B21B 1/22 20060101
B21B001/22; B21B 28/02 20060101 B21B028/02 |
Claims
1. A method for surfacing a work roll for rolling aluminum sheet,
comprising the following steps: indenting a surface of the work
roll with spherical media, producing a surface 60% to 100% covered
by the indentations, the indentations lacking facets.
2. The method of claim 1, wherein the indentations have a depressed
central area relative to a mean height of the surface and a raised,
smooth peripheral lip having a greater height at an apex thereof
than the mean height of the surface.
3. The method of claim 2, wherein the indentations have a diameter
in the range of 200 .mu.m to 400 .mu.m and a depth relative to the
apex of the peripheral lip in the range of 0.5 .mu.m to 2.0
.mu.m.
4. The method of claim 1, wherein the spherical media used for
indenting is steel ball bearings.
5. The method of claim 4, wherein the ball bearings have a diameter
.ltoreq.0.125 inches and a hardness Rc.gtoreq.60.
6. The method of claim 1, wherein the spherical media used for
indenting is ceramic balls.
7. A work roll for rolling aluminum sheet metal surfaced by the
method of claim 1.
8. Aluminum sheet metal having a surface texture imparted by the
work roll of claim 7.
9. A work roll for rolling aluminum sheet metal surfaced by the
method of claim 3.
10. Aluminum sheet metal having a surface texture imparted by the
work roll of claim 9.
11. The method of claim 1, further comprising the steps of:
installing the surfaced work roll in a rolling mill; and rolling
the aluminum sheet to reduce the aluminum sheet from a given
initial thickness to a selected thickness and simultaneously
imparting a texture from the work roll onto the surface of the
aluminum.
12. The method of claim 11, wherein the indentations have a
depressed central area relative to a mean height of the surface and
a raised, smooth peripheral lip having a greater height at an apex
thereof than the mean height of the surface the indentations having
a diameter in the range of 200 .mu.m to 400 .mu.m and a depth
relative to the apex of the peripheral lip in the range of 0.5
.mu.m to 2.0 .mu.m and wherein the reduction in thickness of the
aluminum sheet is in the range of 10 to 60% of the initial
thickness.
13. The method of claim 12, further comprising the step of
pre-grinding the work roll prior to step of surfacing, the step of
pre-grinding imparting a first surface texture on the roll, the
step of surfacing imparting a second surface texture on the roll at
least partially over-struck on the first surface texture and
incompletely eradicating the first surface texture, such that a
composite surface texture is formed.
14. The method of claim 12, wherein the step of indenting is by
shot peening, which may be conducted at an adjustable pressure to
control media velocity and momentum when the media impacts the
roll, the media and the velocity thereof corresponding to a media
impression depth, width and shape on the surface of the roll and
further comprising the step of adjusting the pressure at which shot
peening is conducted to achieve a given surface texture.
15. The method of claim 14, wherein the dwell time of shot peening
of the roll surface is adjustable to control the number of impacts
of the media on the surface of the roll and the consequential %
coverage of media impressions on the surface of the roll and
further comprising the step of adjusting the dwell time to achieve
a given surface texture.
16. The method of claim 14, wherein the surface texture of the roll
is optically diffuse and specular.
17. The method of claim 16, further comprising the steps of rolling
a plurality of sheets of aluminum, the sheets differing in width
and at least one variation in width resulting in rolling a narrower
sheet followed by rolling a wider sheet.
18. The method of claim 16, wherein the adjustment of the velocity
of the media is determined at least partially based upon the
hardness of the roll.
19. The method of claim 16, wherein the adjustment of the velocity
of the media is determined at least partially by the initial
surface texture of the roll prior to shot-peening.
20. A method for surfacing a work roll for rolling aluminum sheet,
comprising the steps of: (A) positioning the work roll parallel
another roll with a gap therebetween; (B) turning at least one of
the work roll and the another roll; (C) feeding surfacing media
into the gap, the media bridging the gap and being drawn through
the gap by the turning work roll and creating impressions on the
surface of the work roll.
21. The method of claim 20, wherein the media has discrete units
having a dimension larger than the gap, such that a mechanical
interference exists when the units pass through the gap.
22. The method of claim 21, wherein the units are spherical and the
impressions are smooth indentations.
23. The method of claim 22, wherein the units are ball
bearings.
24. The method of claim 22, wherein units are joined to a sheet of
flexible material.
25. The method of claim 20, wherein the surfacing media is a metal
shim having a texture on at least one side.
26. The method of claim 25, wherein the shim is produced using
photolithography.
27. A method for surfacing a work roll for rolling aluminum sheet,
comprising the steps of: (A) positioning an ultrasonic ball peening
apparatus proximate the work roll; (B) peening the work roll until
the surface is 60% to 100% covered by indentations lacking facets,
the indentations having a depressed central area relative to a mean
height of the surface and a raised, smooth peripheral lip having a
greater height at an apex thereof than the mean height of the
surface, the indentations having a diameter in the range of 200
.mu.m to 400 .mu.m and a depth relative to the apex of the
peripheral lip in the range of 0.5 .mu.m to 2.0 .mu.m.
28. A method for surfacing a work roll for rolling aluminum sheet,
comprising the steps of: (A) pressing a rotatable knurling wheel
with a peripheral surface texture against a side surface of the
work roll; (B) turning the work roll, inducing the knurling wheel
to turn and impressing the peripheral surface texture into the side
surface of the work roll until the side surface of the work roll is
60% to 100% covered by indentations lacking facets, the
indentations having a depressed central area relative to a mean
height of the surface and a raised, smooth peripheral lip having a
greater height at an apex thereof than the mean height of the
surface, the indentations have a diameter in the range of 200 .mu.m
to 400 .mu.m and a depth relative to the apex of the peripheral lip
in the range of 0.5 .mu.m to 2.0 .mu.m.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation in part
application of U.S. application Ser. No. 13/673,468, entitled
Apparatus and Method for Imparting Selected Topographies to
Aluminum Sheet Metal, filed Nov. 9, 2011, which claims the benefit
of U.S. Provisional Application No. 61/558,504 entitled, Apparatus
and Method for Imparting Selected Topographies to Aluminum Sheet
Metal, filed Nov. 11, 2011. The disclosures of each of the
foregoing applications are incorporated herein by reference in
their entirety for all purposes.
FIELD
[0002] The present invention relates to rolled sheet metal and
surfacing thereof, and more particularly, to methods and apparatus
for producing specific surface textures having associated
frictional and optical characteristics, such as an isotropic
surface on aluminum sheet.
BACKGROUND
[0003] Currently, aluminum sheet producers often use a cold rolling
mill to produce sheet of a desired thickness, width and surface.
Skin/temper rolling mills may also be used with low reductions
(<10%) to produce desired surfaces. The surface of the
cylindrical rolls (work rolls) through which the sheet aluminum
passes may be prepared for a rolling operation by grinding with an
abrasive grinding wheel or belt. Grinding leaves the roll surface
with a directional appearance due to grinding marks (grain), which
are then transferred/imparted to a sheet that is rolled by the
ground work roll. The directional appearance of sheet rolled by
ground work rolls is visible and frequently can be seen through
painted coatings applied to the sheet material or to products made
from the sheet material, such as an automobile body panel.
[0004] Embossing mills are also used to impart a given surface
topography on sheet metal, e.g., to produce non-directional
topographies. Processing sheet in an embossing mill is conducted
after the rolling process and after the sheet has been reduced in
thickness to target dimensions that approximate the final
dimensions of the sheet. Embossing mills are intended to impart
surface texture only, as opposed to having a substantial sizing
effect on the sheet, and therefore operate on sheet that has
already been rolled by the work rolls of a rolling mill. Embossing
sheet in an embossing mill represents additional steps beyond
rolling, requiring additional apparatus, material handling and
managing a greater variety of roll types compared to normal rolling
mills.
SUMMARY
[0005] The present disclosure relates to a method for surfacing a
work roll for rolling aluminum sheet. In accordance with one
approach, the method includes indenting a surface of the work roll
with spherical media, producing a surface 60% to 100% covered by
the indentations, the indentations lacking facets.
[0006] In one approach, the indentations have a depressed central
area relative to a mean height of the surface and a raised, smooth
peripheral lip having a greater height at an apex thereof than the
mean height of the surface.
[0007] In one approach, the indentations have a diameter in the
range of 200 .mu.m to 400 .mu.m and a depth relative to the apex of
the peripheral lip in the range of 0.5 .mu.m to 2.0 .mu.m.
[0008] In one approach, the spherical media used for indenting is
steel ball bearings.
[0009] In one approach, the ball bearings have a diameter
.ltoreq.0.125 inches and a hardness Rc.gtoreq.60.
[0010] In one approach, the spherical media used for indenting is
ceramic balls.
[0011] In one approach, a work roll for rolling aluminum sheet
metal is surfaced with spherical media, producing a surface 60% to
100% covered by the indentations, the indentations lacking
facets.
[0012] In one approach, aluminum sheet metal has a surface texture
imparted by the work roll.
[0013] In one approach, a work roll for rolling aluminum sheet
metal is surfaced by with spherical media, producing a surface 60%
to 100% covered by the indentations, the indentations lacking
facets and having a depressed central area relative to a mean
height of the surface and a raised, smooth peripheral lip having a
greater height at an apex thereof than the mean height of the
surface, the indentations having a diameter in the range of 200
.mu.m to 400 .mu.m and a depth relative to the apex of the
peripheral lip in the range of 0.5 .mu.m to 2.0 .mu.m.
[0014] In one approach, aluminum sheet metal has a surface texture
imparted by the work roll.
[0015] In one approach, the following additional steps are
conducted: installing the surfaced work roll in a rolling mill; and
rolling the aluminum sheet to reduce the aluminum sheet from a
given initial thickness to a selected thickness and simultaneously
imparting a texture from the work roll onto the surface of the
aluminum.
[0016] In one approach, the indentations have a depressed central
area relative to a mean height of the surface and a raised, smooth
peripheral lip having a greater height at an apex thereof than the
mean height of the surface the indentations having a diameter in
the range of 200 .mu.m to 400 .mu.m and a depth relative to the
apex of the peripheral lip in the range of 0.5 .mu.m to 2.0 .mu.m
and wherein the reduction in thickness of the aluminum sheet is in
the range of 10 to 60% of the initial thickness.
[0017] In one approach, the step of pre-grinding the work roll is
conducted prior to surfacing, the step of pre-grinding imparting a
first surface texture on the roll, the step of surfacing imparting
a second surface texture on the roll at least partially over-struck
on the first surface texture and incompletely eradicating the first
surface texture, such that a composite surface texture is
formed.
[0018] In one approach, the step of indenting is by shot peening,
which may be conducted at an adjustable pressure to control media
velocity and momentum when the media impacts the roll, the media
and the velocity thereof corresponding to a media impression depth,
width and shape on the surface of the roll and further comprising
the step of adjusting the pressure at which shot peening is
conducted to achieve a given surface texture.
[0019] In one approach, the dwell time of shot peening of the roll
surface is adjustable to control the number of impacts of the media
on the surface of the roll and the consequential % coverage of
media impressions on the surface of the roll and further comprising
the step of adjusting the dwell time to achieve a given surface
texture.
[0020] In one approach, the surface texture of the roll is
optically diffuse and specular.
[0021] In one approach, the following additional steps are
conducted: rolling a plurality of sheets of aluminum, the sheets
differing in width and at least one variation in width resulting in
rolling a narrower sheet followed by rolling a wider sheet.
[0022] In one approach, the adjustment of the velocity of the media
is determined at least partially based upon the hardness of the
roll.
[0023] In one approach, the adjustment of the velocity of the media
is determined at least partially by the initial surface texture of
the roll prior to shot-peening.
[0024] In one approach, a method for surfacing a work roll for
rolling aluminum sheet includes the steps of: (A) positioning the
work roll parallel another roll with a gap therebetween; (B)
turning at least one of the work roll and the another roll; (C)
feeding surfacing media into the gap, the media bridging the gap
and being drawn through the gap by the turning work roll and
creating impressions on the surface of the work roll.
[0025] In one approach, the media has discrete units having a
dimension larger than the gap, such that a mechanical interference
exists when the units pass through the gap.
[0026] In one approach, the units are spherical and the impressions
are smooth indentations.
[0027] In one approach, the units are ball bearings.
[0028] In one approach, the units are joined to a sheet of flexible
material.
[0029] In one approach, the surfacing media is a metal shim having
a texture on at least one side.
[0030] In one approach, the shim is produced using
photolithography.
[0031] In one approach, a method for surfacing a work roll for
rolling aluminum sheet includes the steps of: (A) positioning an
ultrasonic ball peening apparatus proximate the work roll; (B)
peening the work roll until the surface is 60% to 100% covered by
indentations lacking facets, the indentations having a depressed
central area relative to a mean height of the surface and a raised,
smooth peripheral lip having a greater height at an apex thereof
than the mean height of the surface, the indentations having a
diameter in the range of 200 .mu.m to 400 .mu.m and a depth
relative to the apex of the peripheral lip in the range of 0.5
.mu.m to 2.0 .mu.m.
[0032] In one approach, a method for surfacing a work roll for
rolling aluminum sheet includes the steps of: (A) pressing a
rotatable knurling wheel with a peripheral surface texture against
a side surface of the work roll; (B) turning the work roll,
inducing the knurling wheel to turn and impressing the peripheral
surface texture into the side surface of the work roll until the
side surface of the work roll is 60% to 100% covered by
indentations lacking facets, the indentations having a depressed
central area relative to a mean height of the surface and a raised,
smooth peripheral lip having a greater height at an apex thereof
than the mean height of the surface, the indentations have a
diameter in the range of 200 .mu.m to 400 .mu.m and a depth
relative to the apex of the peripheral lip in the range of 0.5
.mu.m to 2.0 .mu.m.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] For a more complete understanding of the present invention,
reference is made to the following detailed description of
exemplary embodiments considered in conjunction with the
accompanying drawings.
[0034] FIGS. 1a and 1b are a plan view and a perspective (3D) view
graphical mappings, respectively, of surface morphology of a sample
surface of a working roll produced by EDT texturing and as measured
by optical profilometry.
[0035] FIG. 2 is a diagrammatic view of an apparatus for surfacing
a work roll in accordance with an embodiment of the present
disclosure.
[0036] FIG. 3a is a plan view graphical mapping of surface
morphology of a sample surface of a working roll produced by a
process in accordance with an embodiment of the present disclosure
and as measured by optical profilometry. FIG. 3b is an enlarged
view of a fragment of FIG. 3a, and FIGS. 3c and 3d are perspective
graphical mappings of the surfaces shown in FIGS. 3a and 3b,
respectively, as measured by optical profilometry.
[0037] FIGS. 4a and 4b are plan view and perspective (3D) view
graphical mappings, respectively, of surface morphology of a sample
surface of a working roll produced by a process in accordance with
an embodiment of the present disclosure, as measured by optical
profilometry.
[0038] FIG. 5a is a plan view graphical mapping of surface
morphology of a sample of rolled aluminum sheet in accordance with
an embodiment of the present disclosure and rolled by a working
roll produced by a process in accordance with an embodiment of the
present disclosure, as measured by optical profilometry. FIG. 5b is
an enlarged view of a fragment of FIG. 5a, and FIGS. 5c and 5d are
perspective graphical mappings of the surfaces shown in FIGS. 5a
and 5b, respectively, as measured by optical profilometry.
[0039] FIGS. 6a, 6b and 6c are plan view graphical mappings of
surface morphology of three samples of rolled aluminum sheet in
accordance with an embodiment of the present disclosure and rolled
by a working roll produced by a process in accordance with an
embodiment of the present disclosure at 10% reduction, 20%
reduction and 40% reduction, respectively, as measured by optical
profilometry. FIGS. 6d, 6e, and 6f are perspective graphical
mappings of the surfaces shown in FIGS. 6a, 6b and 6c,
respectively, as measured by optical profilometry.
[0040] FIGS. 7a and 7b are photographs of working rolls that have
been surfaced in accordance with an embodiment of the present
invention and FIGS. 7c and 7d are enlarged photographs of fragments
of FIGS. 7a and 7b, respectively.
[0041] FIG. 8 is a graph of the influence of surface texture on the
coefficient of friction.
[0042] FIG. 9 is a schematic diagram of a process for developing a
surface texture in accordance with an exemplary embodiment of the
present disclosure.
[0043] FIG. 10 is a diagrammatic view of an apparatus for surfacing
a work roll in accordance with another embodiment of the present
disclosure.
[0044] FIG. 11 is a diagrammatic view of an apparatus for surfacing
a work roll in accordance with another embodiment of the present
disclosure.
[0045] FIGS. 12 and 13 are perspective and cross-sectional views,
respectively, of a media sheet for surfacing a work roll in
accordance with another embodiment of the present disclosure.
[0046] FIG. 14 is a diagrammatic view of an apparatus for
generating a shim for surfacing a work roll in accordance with
another embodiment of the present disclosure.
[0047] FIG. 15 is a diagrammatic view of an apparatus for surfacing
a work roll in accordance with another embodiment of the present
disclosure.
[0048] FIG. 16 is a diagrammatic view of an apparatus for surfacing
a work roll in accordance with another embodiment of the present
disclosure.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0049] An aspect of the present disclosure is the recognition that
for many applications of sheet metal, it is desirable to have a
uniform, non-directional surface finish, i.e., a surface which
appears isotropic and reflects light diffusely. Further, the
present disclosure recognizes that in addition to appearance
effects, the directionally oriented roughness of a sheet surface
rolled by ground work rolls influences forming processes that may
be used to form the sheet metal into a shaped product, such as an
automobile panel, e.g., attributable to variations in frictional
interaction between the forming tool and the sheet stock due to
directionally oriented grain/grinding patterns in the surface of
the metal sheet that were imparted by the work roll. The present
disclosure also recognizes that a more isotropic surface is
beneficial in conducting some forming processes that operate on
aluminum sheet.
[0050] One method for producing a more isotropic surface on a work
roll that is used to roll aluminum sheet metal (primarily for
automotive sheet) is to surface the roll with an electric discharge
texturing (EDT) machine. An EDT texturing head with multiple
electrodes can be placed near the roll surface to generate an
electric discharge/spark/arc from each electrode to the roll
surface, locally melting the roll surface at each spark location
and inducing the molten steel to form small pools of molten metal
within associated craters. Operation of an EDT machine along the
surface of a rotating roll produces an improved isotropic surface,
but one which features numerous microscopic craters in the range of
up to 100 .mu.m in diameter and with rim heights of up to
15.about.20 .mu.m (FIG. 1).
[0051] Applicants have recognized that the rims of the microscopic
craters formed by the EDT process may be brittle, such that when
the EDT textured rolls are used in a rolling mill, high contact
pressure, e.g., up to 200 ksi, between the work roll, the sheet
and/or the backup roll, can wear down the isotropic texture and
produce debris, which is deposited on the sheet surface, on the
mill and in the lubricant.
[0052] FIG. 1 shows a sample surface morphology of a surface S1 of
an EDT treated working roll used for the rolling of aluminum sheet.
As can be appreciated, the surface morphology could be
characterized as covered with numerous sharp peaks and valleys 5.0
.mu.m in magnitude relative to a reference plane.
[0053] FIG. 2 shows a roll treating apparatus 10 having a cabinet
12 for containing a working roll 14. The working roll 14 may be
supported on bearings 16, 18 to enable turning, e.g., by a motor 20
coupled to the working roll 14. The cabinet 12 also houses a
shot/ball peening nozzle 22 which may be mounted on a gantry 24
that allows the nozzle 22 to be selectively moved and positioned,
e.g., by the action of a motor 26 turning a screw drive or
actuating a chain, rack, cable drive, or actuation via a
motor-driven friction wheel drive associated with the nozzle 22.
The nozzle 22 is fed by a compressor 28 and a media hopper 30. The
nozzle 22 mixes compressed gas, e.g., air, from the compressor 28
and media 32 from the hopper 30, propelling and directing the media
30 against the outer surface S of the roll 14. The media may be in
the form of steel, glass or ceramic balls, abrasive grit or other
blasting/shot peening media, as described further below. A computer
34 may be used to programmatically control: the position of the
nozzle 22 by controlling the motor 26, the rotation of the roll by
controlling motor 20, the operation of the compressor 28 and the
rate of dispensing media 32 from the hopper 30. A vision system 36
may be housed within the cabinet 12 to provide a view of the state
of the surface S in order to ascertain whether a given target
surface texture has been achieved through operation of the action
of the roll treating apparatus 10. This vision system may be
attached to the nozzle 22 or independently moveable on the gantry
24, may include magnification and a shield to protect input
aperture and lens from impact from the media 32. Media 32 that has
been projected through the nozzle 22 may be dispensed through a
funnel portion 38 of the cabinet 12 to a recycling line 40 that
returns the media 32 to the hopper 30, e.g., via a screw feed or a
under the influence of compressed air, a blower or suction. The
cabinet 12 may be provided with a door (not shown) and sight glass
(not shown) to facilitate transfer of the roll 14 in and out of the
cabinet 12 and to monitor the operation of roll treating apparatus
10. The nozzle 22 and compressor 28 may be of a commercial type to
achieve the target peeing intensities to create the desired surface
topography.
[0054] Alternatively, the nozzle 22 may be hand-held, as in
conventional shot-peening apparatus. The compressor 28 and the
nozzle 22 may be changed to obtain the target peening intensity
pressure output, i.e., either manually or under computer control,
to regulate the velocity of media 32 projected from the nozzle 22
to accommodate different types of media 32, as well as to
accommodate various operating conditions, such a roll 14 hardness,
initial surface texture and the type of texture desired for surface
S, e.g., attributable to the depth and circumference of
dimples/craters made in the surface of the roll by a given media
32, such as steel balls/shot. The number of impacts and the
dimensions of the impressions made by the media on the roll surface
area relative to the total area can be described as, "% coverage"
and can be adjusted by the compressor output setting, media flow
rate and traverse speed of the nozzle 22 relative to the roll 14,
as the nozzle 22 passes over the roll 14 and/or as the roll 14 is
spun by motor 20. The control of the shot-peening process can be
automatic or manual. For example, a person can manually hold,
position and move the nozzle 22 and or the roll 14, as in
traditional shot-peening operations wherein the person is equipped
with protective gear and partially or fully enters into a cabinet
containing the work piece. Visual or microscopic inspection of the
roll may be conducted to verify suitable operation or to adjust the
apparatus 10 and to verify an acceptably surfaced roll 14 at the
completion of the peening/blasting operation.
[0055] As another alternative, the nozzle 22 may be contained
within a portable, open-sided vessel (not shown) that presses
against the surface S forming a moveable peening chamber that
captures and redirects spent media back to a storage reservoir like
hopper 30. This peening chamber may be positioned and moved
manually or mechanically, such as, by a motor-driven feed mechanism
like gantry 24 and optionally under the control of a computer
34.
[0056] The apparatus and methods of the present disclosure may be
used to surface a working roll that imparts a given desired surface
to sheet as it is rolled to size, e.g., to provide a sheet with an
isotropically diffuse or bright appearance, eliminating the need to
emboss or use a temper pass to create a textured sheet. In this
context, "bright" refers to specular and "diffuse" refers to a
non-specular appearance. The surface textures can be varied to
achieve a given desired appearance and forming functionality
associated with frictional properties by the appropriate choice of
media and operating parameters.
[0057] In accordance with one aspect of the present disclosure, the
desired texture is applied to a work roll surface, e.g. S, by a
peening/blasting process that propels the selected media at the
work roll surface S through a nozzle 22 by air pressure. The
pressure, processing time per unit area, e.g., as a function of
work roll 14 rotation speed and nozzle 22 traverse speed, nozzle 22
configuration and media 32 type are controlled to produce the
desired work roll texture, which is effected by media 32 size,
shape, density, hardness, velocity and resultant dimple/crater or
indentation depth, width and shape and % coverage of
dimples/craters on the treated surface area S. In accordance with
some embodiments of the present disclosure, the media 32 chosen
include spherical indenting media that produces smooth craters,
such as high quality, precision steel ball bearings or shot, beads
(glass, ceramic). Mixtures of beads and grit, such as aluminum
oxide, silicon carbide or other grit types may be used depending
upon the properties desired in the resultant surface.
[0058] FIGS. 3a-3d show graphical mappings of surface morphology as
measured by optical profilometry of a work roll surface that has
been surfaced in accordance with an embodiment of the present
disclosure. The surface S.sub.3 shown in FIGS. 3a-3d has been
peened with steel ball bearings of grade 1000 with a diameter of
.ltoreq.0.125'' and a hardness of Rc.gtoreq.60. Grade 1000 has
0.001'' spherical and .+-.0.005'' size tolerances. Better grades of
ball bearings may also be used. The stand-off distance of the
nozzle 22 from the roll 14 may be about 1 inch to about 12 inches,
with a stand-off of about 5 inches being preferred for some
applications. As can be appreciated, the use of ball bearings as
peening media results in uniformly shaped craters on the work roll
surface and the absence of the sharp, raised lips that are typical
of EDT textures. More particularly, the use of spherical indenting
media creates a plurality of smooth, central depressions mimicking
the shape of the spheres/balls that make them, along with a smooth
peripheral upwelling or lip around the depressions formed by the
displacement of material from the depressions. Along the surface
there is a gradual change in slope and abrupt ledges or
discontinuities are minimized. In general, the depth of each
depression at the center is below the mean or average height of the
surface and apex of the peripheral lip is above the mean height. In
order to make a smooth surface, the spherical indenting media must
not be friable at the level of force required to create crators of
appropriate depth. Otherwise, the spherical media will fracture and
resultant sharp edges and flat facets on the broken media will
cause the formation of facets on the surface of the work roll.
These faceted impressions can occur on impact or later on when the
spherical media is recycled and re-impacted against the surface. In
addition to avoiding breakage of spherical media, it is beneficial
if the force exerted by the media, considering the size, velocity
and density of the spheres, does not create a trajectory upon
impact that results in the formation of lateral furrows having a
significant component of direction parallel to the surface of the
work roll.
[0059] The generally smooth undulations in the surface S.sub.3 of
the work roll have a magnitude typically within the range of +/-3
to 6 .mu.m, however, craters of any desired magnitude, e.g., in
excess of 10 .mu.m or less than 3 .mu.m, may be achieved, as
desired. As described more fully below, the smooth undulating
surface produced by spherical indenting media, such as ball
bearings may be produced in random patterns, e.g., as would be
expected of a shot peening operation or in discrete patterns, as
explained below. A typical EDT surface has a greater number of
severe surface variations. A work roll shot-peened with ball
bearings, as described above, can be used to produce bright sheet
with an isotropic appearance, depending upon the starting
background roll surface. While grade 1000 ball bearings were
described above, other types of precision balls may be used,
depending upon roll hardness, such as higher grade ball bearings.
As noted, the spherical media selected for indenting the surface of
the roll are preferably selected with material properties, such as,
density, hardness, elasticity, compression strength and tensile
strength that allow the balls to impact and indent a roll of a
given hardness without breaking or developing facets due to the
impact.
[0060] FIGS. 4a and 4b show a work roll surface S.sub.4 produced in
accordance with another embodiment of the present disclosure. More
particularly, FIG. 4a is a plan view as measured by optical
profilometry of the topology of a work roll surface that has been
peened with aluminum oxide grit mixture (2:3 ratio of 120:180 grit)
followed by glass beads of grade AC (60-120 mesh). The aluminum
oxide grit blasting was carried out in a manner to remove the
pre-grind roll pattern (as ascertained by visual evaluation),
followed by blasting with the glass beads to achieve a desired
diffuse surface appearance. FIG. 4b is a perspective (3D) graphical
mapping of surface morphology of the surface S.sub.4 shown in FIG.
4a, as measured by optical profilometry. As can be appreciated from
FIGS. 4a and 4b, the use of glass beads results in a surface
S.sub.4 having fewer severe peaks than an EDT surface and the
magnitude of surface variations is smaller than an EDT surface.
FIG. 4b shows surface variations in the approximate range of +/-2.0
.mu.m. Accordingly, one could fairly characterize the resultant
surface S.sub.4 as smoother than an EDT surface, but still having a
micro-roughness which may be used to impart a diffuse isotropic
surface appearance to an aluminum sheet that is rolled by a working
roll having this type of surface.
[0061] In accordance with the present disclosure, surface treatment
of a work roll by peening results in a surface which is less
brittle than a work roll surface treated by the EDT process. As a
result, the work roll surface (texture) lasts longer, can sustain
higher surface loading pressures and creates less debris when used
in rolling operations. In accordance with an embodiment of the
present disclosure, where spherical media, such as ball bearings or
glass beads, are used to surface the work roll, the gently
undulating surface texture produced on the work roll provides
advantages in the rolling process to produce an isotropic surface.
Compared to normal, ground work rolls or EDT surfaced work rolls,
the gentle undulations promote lower friction between the sheet and
the working rolls, enabling higher reductions in sheet thickness to
be conducted before lubricant or roll surface failure. The texture
of a work roll surfaced in accordance wih the present disclosure
does not wear at the same rate as a typical ground work roll or an
EDT surfaced roll. Experiments have shown that in a work
roll-driven mill, the textures imparted to the roll by the methods
of the present disclosure last 5 to 6 times longer than normally
ground roll surfaces and that higher reductions are possible than
those taken by EDT working rolls before exceeding mill horsepower
limitations and experiencing lubricant failure. A roll surface
morphology generated in accordance with an embodiment of the
present disclosure can withstand greater than a 10% thickness
reduction ratio to produce the desired textured sheet, e.g., up to
60%. This is in contrast to EDT surfaced working rolls which are
typically operated in a range of about 8% to 10% reduction. Taking
higher reductions can potentially allow elimination of an otherwise
necessary pass(es) through the rolling mill to achieve the desired
thickness.
[0062] FIG. 5a shows a sample surface AS.sub.5 of a rolled aluminum
sheet in accordance with the present disclosure and rolled by a
working roll 14 with a roll surface, such as the roll surface
S.sub.3 illustrated in FIGS. 3a-3d, produced by a process in
accordance with an embodiment of the present disclosure. FIG. 5b is
enlarged view of the surface shown in FIG. 5a, both being rendered
by optical profilometry. FIGS. 5c and 5d are perspective (3D)
graphical mappings of the sample imaged in FIGS. 5a and 5b as
measured by optical profilometry. The sheet produced as illustrated
in FIGS. 5a-5d were produced by shot-peening with precision steel
ball bearings. As illustrated and in general, the macro-texture,
e.g., peened dimples/indentations, imparted to sheet metal by the
working rolls during rolling is the inverse of the texture on the
work roll. However, both macro and micro features affect the final
level of surface brightness, i.e., the final level of specular
reflection, of the sheet.
[0063] FIGS. 6a, 6b and 6c show plan view graphical mappings of
surface morphology of three surface samples AS.sub.6a, AS.sub.6b
and AS.sub.6c of rolled aluminum sheet in accordance with an
embodiment of the present disclosure and rolled by a working roll
produced by a process in accordance with an embodiment of the
present disclosure at 10% reduction, 20% reduction and 40%
reduction, respectively, and as measured by optical profilometry.
The working roll used to roll these samples was surfaced by
shot-peening with aluminum oxide grit followed by shot-peening with
glass beads, as described above relative to FIGS. 4a and 4b. FIGS.
6d, 6e, and 6f are perspective graphical mappings of the surfaces
shown in FIGS. 6a, 6b and 6c, respectively, as measured by optical
profilometry.
[0064] FIGS. 7a and 7b are photographs of working rolls that have
been surfaced in accordance with an embodiment of the present
invention. FIGS. 7c and 7d are enlarged photographs of fragments of
FIGS. 7a and 7b, respectively. The roll shown in FIGS. 7a and 7c
were shot-peened with class 1000 steel ball bearings of 1.6 mm in
diameter. The roll was shot-peened under conditions that produced
100% coverage of the surface S.sub.7a of the roll with
dimples/indentations. The roll shown in FIGS. 7b and 7d were
shot-peened with class 1000 steel ball bearings of 2.36 mm in
diameter. The roll was shot-peened under conditions that produced
50% coverage of the surface S.sub.7b of the roll with dimples.
[0065] In accordance with an embodiment of the present disclosure,
sheet can be produced through normal rolling production schedules,
eliminating the need to emboss or use a temper pass on the rolling
mill. The resultant work roll surface textures do not wear as fast
as EDT produced and normal ground roll surfaces. As a result, roll
life exceeds 5 to 6 times that of normal rolls. On a work
roll-driven mill, production is not limited to wide-to-narrow
production schedules since the texture does not develop banding due
to wear. As noted above, the sheet produced by a work roll surface
shot-peened with, e.g., ball bearings, generates less debris than
an EDT surfaced or normal ground surface, resulting in cleaner
lubricant and sheet during rolling. The resultant sheet is
isotropic in appearance.
[0066] FIG. 8 shows the directionally dependent coefficient of
friction during a forming operation of various surfaces when
forming is performed in longitudinal (L) and transverse (T)
directions. As to the sample 6022-T43, the peened surface showed a
reduction in friction on average and a smaller variation in
friction dependent upon the direction of forming. Isotropic
frictional interaction with forming tools, such as those used in
drawing and ironing may represent an improvement in forming
performance, e.g., producing more uniform drawing and extended
drawing limits.
[0067] In accordance with the present disclosure, the initial
surface finish requirements for the work roll before peening, e.g.,
with ball bearings, depends on the final sheet appearance
requirement, e.g., highly specular or somewhat specular. The
background roughness is preferred to be <1 .mu.in if a highly
specular isotropic surface is desired. If a less specular surface
is required, the initial work roll grind can be any desired grind
up to 50 .mu.in. The amount of pre-grind desired impacts the final
cost of the entire process since it is generally more expensive to
produce a surface finish <1 .mu.in roughness. The initial
surface finish requirements for the work roll before peening with
glass beads or other media to produce a diffuse surface is
preferred to be <15 .mu.in or a roughness such that the roll
grind pattern is not visible on the peened work roll after
processing. The removal of the background roll grind during glass
bead peening will be dependent upon the peening processing
parameters chosen to produce the diffuse finish. The present
disclosure is further illustrated by the following examples.
Example 1
[0068] FIGS. 3a-d, 7a and 7c show images of an exemplary surface
S.sub.3, S.sub.7a of a working roll made in accordance with an
exemplary embodiment of the present disclosure. To generate the
surface shown, a background roll topography is created with
standard grinding processes (pre-grind) of about <5 .mu.in
roughness. A series of dimples ranging in diameter from 200 to 300
.mu.m are produced on the roll surface by shot-peening with class
1000 steel balls of 1.6 mm in diameter and hardness Rc.gtoreq.60.
The balls are propelled against the surface of a roll having a
hardness of about 58 to 62 Rc, at a velocity causing a dimple
diameter of about 200 .mu.m to 400 .mu.m and a dimple depth of
about 0.5 .mu.m to about 4 .mu.m. Dimple diameter and depth are
affected by processing conditions (ball velocity) and are dependent
upon the initial work roll hardness. In this example, about 100% of
the surface area is covered by dimples, as measured by visual
inspection, but coverage can range from about 10% to about 250%,
depending upon the desired surface appearance finish. A coverage of
60% to 100% provides a work roll surface that produces aluminum
sheets with desirable optical and mechanical properties. The %
coverage measured can vary depending upon the method of measuring.
Optical methods tend to over-estimate coverage when compared to
physical measurement from topographical images.
[0069] The benefits experienced with use of these rolls in
breakdown rolling include: pass elimination (1 pass eliminated in
cold rolling, 3 passes eliminated in hot rolling); the ability to
roll narrow to wide; increased roll life; less roll coating
developed in hot rolling due to reduced material transfer; and
reduced debris generation in cold rolling.
Example 2
[0070] In accordance with another exemplary embodiment of the
present disclosure, a diffuse surface work roll may be made by
peening a working roll that is pre-ground at <5 microinch
roughness The media may be glass bead, other "ceramic" beads of
grade A to AH which are mesh sizes 20-30 to 170-325 or other hard
abrasive particles, such as aluminum oxide (grit sizes to 12 to
400). A combination of glass beads, ceramic beads and aluminum
oxide media, applied in succession, may be required to produce a
surface finish like that shown in FIGS. 4a and 4b. For example, the
roll surface is first processed with aluminum oxide of mixed grit
sizes (2:3 ratio of 120 and 180 grits) with a 5/16'' nozzle and 65
PSI at a traverse speed of 1.5'' per minute followed by glass beads
grade AC (mesh size 60-120) at 100 PSI using a 3/8'' nozzle and
traverse speed of 1.5'' per minute. The standoff distance was
adjusted based on the nozzle bristle lengths of the particular
peening system. Choices of nozzles, pressures and traverse speeds
would be dependent upon the apparatus used to peen. The percent
area of coverage can range from 10% to 250% depending upon the
desired surface finish.
[0071] A working roll surfaced in accordance with the above
parameters may be operated at reductions between 10 to 60% (in
contrast to EDT treated rolls which are typically operated at
reduction of about 8% to 10%). The higher level of reduction may be
utilized to eliminate one or more reduction passes that might
otherwise be required to achieve a desired thickness and surface
appearance. The resultant sheet has an isotropic appearance and
isotropic functionality.
[0072] FIG. 9 shows a diagram of a process for developing a surface
texture in accordance with an exemplary embodiment of the present
disclosure. In a first stage (I) (not shown), the surface
topologies that are obtained by using a range of peening conditions
and media types are predicted. For a work roll surface treated by
shot-peening, the media size, composition and peening process
conditions, such as velocity and % coverage, may be selected to
control the desired final texture of the roll, which is then
imparted to the rolled product. The relationships between these
variables (media size, composition and peening process conditions)
and the surfacing results obtained may be recorded and used as a
basis for predictive computer modeling at stage I for any given set
of parameters to produce the roll surface texture.
[0073] In the next stage (II) (shown in FIG. 9), the light scatter
and appearance for a given set of real or hypothesized surface
topographies are predicted. As shown in FIG. 9, modeling may
include selecting a "target" surface which has specific optical
properties, such as predicted light scatter, e.g., to yield a given
degree of brightness. A method for generating aluminum sheet having
the desired optical properties may then be pursued by the following
steps.
[0074] (A) accumulating a data file which associates a plurality of
given surface profiles with corresponding optical properties of
each surface profile, including light scatter, length scale and
surfacing treatment parameters utilized to realize each of the
plurality of surfaces; (B) implicitly prescribing a virtual surface
by specifying target optical properties; (C) modeling the virtual
surface by retrieving data pertaining to at least one surface
profile with the most similar measured or predicted optical
properties as the target optical properties; (D) comparing the
target optical properties to the optical properties of the at least
one surface profile; (E) in the event that the comparison in step
(D) does not indicate identity, then retrieving data pertaining to
another surface profile in the data file that has measured or
predicted optical properties that are similar to the target
properties but are at variance to the target properties in an
opposite respect relative to how the optical properties of the at
least one given surface profile differ from the target properties;
(F) sampling from the optical properties of the at least one
surface profile and from another surface profile in proportion to
the magnitude of their respective differences from the target
properties to arrive at corrected optical properties of a corrected
virtual surface and recording the composited sampled composition
contributions of the at least one surface profile and the other
surface profile; (G) comparing the optical properties of the
corrected virtual surface to the target optical properties to
ascertain the reduction in the differences there between; and then
repeating the steps (E)-(G) until little or no improvement is
discerned, whereupon the best virtual surface relative to the
target has been ascertained.
[0075] Note that steps (C) through (G) can be executed as described
or can be replaced by a non-linear least squares optimization
algorithm to automate the process. To complete the process, the
Modeling steps (I) and (II) are combined. Namely, by: (1)
ascertaining the surfacing treatment parameters utilized to realize
each of the plurality of surfaces by compositing such parameters in
proportion to the contribution of optical properties of each
surface profile composited in the best virtual surface thereby
defining best surfacing treatment parameters; (2) conducting
surfacing of a roll in accordance with the best surfacing treatment
parameters; and (3) rolling the aluminum sheet with the roll
surfaced at step (I). As can be seen, upon reaching a modeled
solution, the shot-peening parameters associated there with may be
implemented in surfacing a work roll. The actual results of
implementation may be stored in the database along with the process
parameters that caused them to expand the modeling capability.
[0076] FIG. 10 shows an alternative apparatus 110 for surfacing
work rolls 114a, 114b in accordance with another embodiment of the
present disclosure. During the surfacing process to be described
below, the work rolls 114a, 114b are arranged in parallel and are
rotatable relative to each other, being supported on the ends by
suitable bearings (not shown), like 16, 18 of FIG. 2 and driven by
a motor or motors (not shown) like motor 20 shown in FIG. 2. A
media nozzle 122 like nozzle 22 of FIG. 2 may be retained on a
gantry for moving or positioning the nozzle 122 along the length of
the rolls 114a, 114b proximate to where they converge, which may be
called a nip N. The nozzle 122 can dispense media, e.g., ball
bearings 132 into the nip area N, such that when the rolls 114a,
114b are turned in the directions shown by the arrows, the balls
132 will be drawn between the rolls. Unlike nozzle 22, the nozzle
122 need not propel the balls 132 under pressure to achieve a high
velocity, but may merely dispense the balls 132 in a controlled
manner. If the space between the rolls 114a, 114b is smaller than
the diameter of the balls 132, then a state of mechanical
interference is achieved when they are drawn into the nip N. Given
that the balls 132 are of comparable or greater hardness than the
surface of the rolls 114a, 114b and are sufficiently elastic,
having an adequate compression strength to pass through the nip N
without breaking, they will induce the formation of craters in the
surface of the rolls 114a, 114b as they pass through the nip N. The
craters are formed in the surface of the rolls 114a, 114b by
compression rather than from the force of impact of balls projected
at the surface at high velocity. After passing through the nip N,
the balls 132 may be collected in a gutter or hopper 138 for
re-use. The rolls 114a, 114b may be adjustable to allow them to be
moved closer together or farther apart, narrowing or widening the
nip N, to adjust to different size balls 132 and/or to control the
depth of the craters that are formed on the rolls 114a, 114b.
[0077] FIG. 11 shows a similar apparatus as FIG. 10 with another
type of ball feeding mechanism, viz., an elongated hopper/funnel
230, which is capable of holding and dispensing a supply of balls
232, such that the area between the nip N and the hopper/funnel 230
is filled to capacity with balls 132 at all times. More
particularly, balls 232 passing through the nip act as a stopper
line causing balls falling through the hopper funnel 230 to back up
and prevent more balls from falling out. The funnel/hopper 230 may
be closely fitted to the generally V-shaped area defined by the
rolls 214a, 214b above the nip N, such that balls 232 can not pass
between the rolls 214a, 214b and the funnel/hopper 230. As balls
232 pass through the nip N, more balls flow out of the
hopper/funnel 230 to replace them. The used balls 232 are collected
in gutter 238 and recycled via lines 240a, 240c and recycling
apparatus 240b. A barrier 242 on either end of the rolls 214a, 214b
(only one shown) can be used to prevent the balls 232 from flowing
over the ends of the rolls 214a, 214b, containing the balls 232 in
the V-shaped area.
[0078] FIGS. 12 and 13 show a media sheet 344 for surfacing a work
roll in accordance with another embodiment of the present
disclosure. The media sheet 344 may have a web portion 344a, e.g.,
made from an elastomer, in which surfacing media, such as spherical
indentors 332 like ball bearings are embedded. Alternatively, the
web portion 344a could be made from a sheet of paper or polymer to
which the surfacing media is adhered by glue. The media sheet 344
may be employed with a surfacing apparatus 110, 210 like those
shown in FIGS. 10 and 11, namely, by passing the media sheet 344
through the nip N in place of loose balls 132, 232. If the web
portion 344a is resilient enough and holds the balls 332 tightly,
it may be possible to make a continuous loop with the media sheet
344 allowing it to be cycled between the rolls 214a, 214b until the
desired crater coverage is realized. As shown in FIG. 12, the balls
332 may be distributed over the media sheet 344 in any desired
pattern, such as a comprehensive, evenly spaced coverage of the
entire media sheet 344, a more dispersed pattern or a random
distribution.
[0079] FIG. 14 diagrammatically shows a support surface 446, e.g.,
glass, coated with a layer of photoresist or a photopolymer 448. A
source of radiation 452, such as a UV light, an electron beam or a
laser, emits radiation, R1. In the case of light, an optional
radiation distribution element 450, such as a mask or a lens array,
distributes the radiation R1 into a distributed array of radiation
R2 that impinges on the photoresist layer 448 creating an
undulating pattern 448a of greater and lesser light exposure. Upon
development of the photoresist, a surface having a desired smoothly
contoured texture may be formed. Alternatively, the layer of
photoresist may be exposed/shaped by a laser scanner or electron
beam scanner to generate the desired pattern of exposure and
resultant surface profile upon development.
[0080] As described in U.S. Pat. No. 7,094,502 to Schaefer et al.,
which is owned by the assignee of the present application and which
is incorporated herein in its entirety by reference, a shim 453 may
be grown from the surface profile of the developed photoresist
layer 448. As further described in U.S. Pat. No. 7,094,502, the
shim 453 may be hardened via various plating and coating processes
to allow it to impressed upon the surface of a metal roll to allow
the surface texture thereof to be transferred to the surface of the
roll, and then, subsequently, to a product surface. In accordance
with one aspect of the present disclosure, a shim 453 having a
smoothly undulating surface profile may be used to impart that
texture to a working roll, like roll 114a and or 114b. For example,
a shim 453 of this nature could be used like the media sheet 344,
passing the shim 453 between rolls 214a, 214b of the apparatus 210
of FIG. 11. In order to surface both rolls 214a, 214b
simultaneously, two shims 453 placed back to back or a shim 453
with two textured faces could be employed. As another alternative,
a textured shim 453 could be affixed to the surface of a work roll,
e.g., 214a by adhering it to the roll via adhesives, brazing or
welding and then used to roll aluminum sheet.
[0081] FIG. 15 diagrammatically shows an ultrasonic ball peening
apparatus 510 for surfacing a work roll 514 in accordance with
another embodiment of the present disclosure. Ultrasonic ball
peening devices are available commercially, e.g., from Sonats SA,
Nantes, Carquefou, France. In accordance with the present
disclosure, such ball peening devices may be applied to the purpose
of surfacing working rolls for rolling sheet aluminum, i.e., if the
velocity, density, size, elasticity, and compression strength of
the balls are such that the appropriate crater depth is realized on
the surface of the treated roll without peening media
breakage/degradation.
[0082] FIG. 16 shows an apparatus 610 for surfacing a work roll 614
in accordance with another embodiment of the present disclosure. A
knurling head 662 supports a knurling wheel 664 having a textured
surface 664a. The knurling wheel 664 is rotatable on an axle 664b
and is urged into the surface of the work roll 614 under the
influence of a substantial force F. Since the contact area of the
knurling wheel 664 and the work roll 614 is very small, the force F
is concentrated over a small area, allowing the texture of the
surface 664a to be transmitted to the roll 614, as shown by the
area 614a. A gantry 624 may be used to allow the knurling head 662
to traverse the work roll 614 to impart the desired texture over
the entire roll 614. The work roll 614 may be rotated by an
electric motor inducing the knurling wheel 664 to rotate as it
textures the work roll 614. An aspect of the present disclosure is
to ensure that the resultant surface 614a (or the resultant
surfaces of a work roll processed by the apparatus described with
reference to FIGS. 10-15) has a conformation consistent with the
beneficial texture described above, e.g., that achieved by shot
peening with ball bearings, such as described above referring to
FIGS. 3a-3d. The texturing of a work roll 614 using the apparatus
610 may require more than one traversal by the knurling head 662,
depending upon the density of the surface texture of the surface
664a (undulations per unit area) and the coverage % desired.
[0083] It will be understood that the embodiments described herein
are merely exemplary and that a person skilled in the art may make
many variations and modifications without departing from the spirit
and scope of the claimed subject matter. For example, some
disclosure above indicated that the range of roughnesses (roll
grind) that are typically applied to aluminum rolling operations
covering hot and cold rolling applications span <1 .mu.in to 50
.mu.in and that typical work roll hardnesses for A1 operations is
50 to 70 Rc. Notwithstanding, the methods and apparatus of the
present disclosure could be applied to any surface finish above 50
.mu.in and any roll hardness to achieve the same results by
adjusting the peening media and peening parameters, such as
pressure and dwell time to affect % coverage. All such variations
and modifications are intended to be included within the scope of
the present disclosure.
* * * * *