U.S. patent application number 12/123026 was filed with the patent office on 2008-11-13 for composite metal article and method of making.
This patent application is currently assigned to WILLIAM ENGINEERING LLC. Invention is credited to Gregg Anthony DION, Paul Armand DION.
Application Number | 20080277454 12/123026 |
Document ID | / |
Family ID | 30770425 |
Filed Date | 2008-11-13 |
United States Patent
Application |
20080277454 |
Kind Code |
A1 |
DION; Paul Armand ; et
al. |
November 13, 2008 |
COMPOSITE METAL ARTICLE AND METHOD OF MAKING
Abstract
A composite metal article from two dissimilar metals is
prepared. A metal base is comprised of a first metal and having
first and second opposing surfaces and a least one
longitudinally-positioned depression in each of the first and
second opposing surfaces for receiving a wire. An elongated metal
element comprised of a second metal is introduced into each of the
at least one first and second depressions of the metal base to form
a composite assembly, and the composite assembly is heated under
pressure to urge the adjacent surfaces of the second metal elements
and the depressions together to form a bonded article.
Inventors: |
DION; Paul Armand; (North
Attleboro, MA) ; DION; Gregg Anthony; (North
Attleboro, MA) |
Correspondence
Address: |
WILMERHALE/BOSTON
60 STATE STREET
BOSTON
MA
02109
US
|
Assignee: |
WILLIAM ENGINEERING LLC
Attleboro
MA
|
Family ID: |
30770425 |
Appl. No.: |
12/123026 |
Filed: |
May 19, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10207409 |
Jul 29, 2002 |
7373857 |
|
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12123026 |
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Current U.S.
Class: |
228/158 ;
228/212 |
Current CPC
Class: |
B21B 27/03 20130101;
B21B 37/52 20130101; B21B 45/004 20130101; B21B 2015/0021 20130101;
B23K 20/04 20130101; B23K 2101/34 20180801; B21B 13/12 20130101;
Y10T 428/1234 20150115; B21K 11/02 20130101; B23K 2103/04 20180801;
B21B 2027/083 20130101; B23K 2103/16 20180801; B21B 27/00 20130101;
B23D 61/125 20130101; B23K 20/023 20130101; B21B 27/02 20130101;
B21B 3/02 20130101; B23K 20/02 20130101; B21B 9/00 20130101; B21B
2265/06 20130101; B21B 2001/383 20130101; B26B 9/02 20130101; B23D
65/00 20130101; B21B 13/103 20130101 |
Class at
Publication: |
228/158 ;
228/212 |
International
Class: |
B23K 31/02 20060101
B23K031/02 |
Claims
1. A method of making a composite article, comprising: (a)
providing a metal base comprised of a first metal and having first
and second opposing surfaces, said base having at least one
longitudinal depression in at least one of said first and second
opposing surfaces; (b) introducing a wire comprised of a second
metal into said at least one depression of the metal base to form a
composite assembly, said second metal comprising a cutting tool
grade steel and being harder than the first metal; (c) heating the
composite assembly under pressure to urge the adjacent surfaces of
the wire and the at least one depression together to form a bonded
article and to reduce the thickness of the metal base at least at
the wire/base interface; and (d) constraining a lateral spread of
the composite assembly during at least a portion of the step of
heating under pressure under conditions to maintain a lateral
bonding pressure on the composite assembly.
2. The method of claim 1, wherein the step of heating the composite
assembly under pressure in step (c) comprises reducing the
thickness of the metal base to the extent that a transverse
cross-section of at least a portion of the bonded article includes
substantially no first metal.
3. The method of claim 1, wherein the step of heating the composite
assembly under pressure in step (c) comprises reducing the
thickness of the metal base to 1 to 70% of a transverse
cross-section of the article at the metal base's thinnest
point.
4. The method of claim 1, wherein a pair of metal bases is
provided, each metal base having at least one longitudinal
depression, and the wire is introduced into the longitudinal
depression of each metal base.
5. The method of claim 1, wherein the constraining step (d) is
carried out using a mated pair of male/female rolls.
6. The method of claim 1, wherein the step of providing a metal
base having at least one longitudinal depression in step (a)
comprises providing the at least one depression in the form
selected from the group consisting of v-groove, square groove,
rounded groove, and rectangular groove.
7. The method of claim 1, wherein the step of providing a metal
base having at least one longitudinal depression in step (a)
comprises providing at least one depression located in the center
of the first opposing surface of the metal base.
8. The method of claim 1, wherein the step of providing a metal
base having at least one longitudinal depression in step (a)
comprises providing at least one depression offset from the center
of the first opposing surface of the metal base.
9. The method of claim 1, wherein the step of providing a metal
base comprises providing the first metal selected from the group
consisting of hot or cold rolled metal or metal alloys that are
spring-like.
10. The method of claim 1, wherein the second metal is selected
from the group consisting of high speed steels.
11. The method of claim 1, comprising forming a metallurgical bond
between the first and second metals.
12. The method of claim 1, wherein the constraining step (d) is
carried out using a turks head.
13. The method of claim 12, wherein side rolls of the turks head
are forward offset at a distance from a set of bonding rolls at an
entrance side of said bonding rolls, so that the side rolls of the
turks head apply an opposing force to the composite assembly to
constrain lateral spread of the composite assembly.
14. The method of claim 1, wherein the step of providing a metal
base in step (a) comprises providing a sheet or strip.
15. The method of claim 14, wherein the step of providing a sheet
or strip comprises providing a sheet having an aspect ratio of
greater than 5:1.
16. The method of claim 1, wherein the metal base includes
depressions in the first and second surfaces, said metal base
having a cross-section with an appearance of a barbell.
17. The method of claim 16, wherein the metal base has an aspect
ratio of about 1:1 to about 1:10.
18. The method of claim 1, further comprising rolling the composite
assembly to form a rectangular bar.
19. The method of claim 18, further comprising trimming an edge of
the bar to expose an interior surface comprising the second
metal.
20. The method of claim 1, wherein the wire has a cross-sectional
shape selected from the group consisting of round, square, oval,
polygonal, rectangular, and rhomboid.
21. The method of claim 20, comprising providing the at least one
longitudinal depression of the metal base of step (a) in a shape
that is complementary to the shape of the wire of step (b).
22. The method of claim 1, wherein the wire is a composite metal
wire.
23. The method of claim 22, wherein the composite metal wire
comprises upper and lower regions comprised of the second metal and
at least one inner region disposed between the upper and lower
regions comprised of a third metal.
24. The method of claim 23, wherein the third metal is different
than the first metal.
25. The method of claim 23, wherein the third metal is the same as
the first metal.
26. The method of claim 22, wherein the composite wire is made by:
contacting a first metal member and a second metal member under
heat and pressure to urge the adjacent surfaces of the first and
second metal members together to form a bonded wire.
27. The method of claim 1, wherein the step of providing a metal
base in step (a) comprises providing a metal base having at least
one depression on each of said first and second surfaces.
28. The method of claim 27, wherein the step of providing a metal
base in step (a) comprises providing the depression of the first
opposing surface and the depression of the second opposing surface
opposite one another.
29. The method of claim 27, wherein the constraining step (d) is
carried out using a mated pair of male/female rolls.
30. The method of claim 27, wherein the step of providing a metal
base in step (a) comprises providing the at least one depression in
the form selected from the group consisting of v-groove, square
groove, rounded groove, and rectangular groove.
31. The method of claim 27, wherein the constraining step (d) is
carried out using a turks head.
32. The method of claim 31, wherein side rolls of the turks head
are forward offset at a distance from a set of bonding rolls at an
entrance side of said bonding rolls, so that the side rolls of the
turks head apply an opposing force to the composite assembly to
constrain lateral spread of the composite assembly.
33. The method of claim 27, wherein the wire has a cross-sectional
shape selected from the group consisting of round, square, oval,
polygonal, rectangular, and rhomboid.
34. The method of claim 33, comprising providing the at least one
longitudinal depression of the metal base of step (a) in a shape
that is complementary to the shape of the wire of step (b).
35. The method of claim 27, wherein the wire is a composite metal
wire.
36. The method of claim 35, wherein the composite metal wire
comprises upper and lower regions comprised of the second metal and
at least one inner region disposed between the upper and lower
regions comprised of a third metal.
37. The method of claim 36, wherein the third metal is different
than the first metal.
38. The method of claim 36, wherein the third metal is the same as
the first metal.
39. The method of claim 35, wherein the composite wire is made by:
contacting a first metal member and a second metal member under
heat and pressure to urge the adjacent surfaces of the first and
second metal members together to form a bonded wire.
40. The method of claim 27, wherein the step of providing a metal
base in step (a) comprises providing at least one depression offset
from the center of the first opposing surface of the metal
base.
41. The method of claim 27, wherein applying pressure in step (c)
is accomplished by rolling or swaging.
42. The method of claim 41, wherein applying pressure is
accomplished by rolling.
43. The method of claim 42, wherein said rolling comprises a
plurality of rolling steps.
44. The method of claim 43, wherein the bond strength between the
wire and the metal base increases during the plurality of rolling
steps.
45. The method of claim 43, wherein said rolling comprises 2-10
rolling steps.
46. The method of claim 43, wherein said rolling comprises 3-6
rolling steps.
47. The method of claim 43, wherein at least a first rolling step
consolidates the composite assembly and constrains lateral
spread.
48. The method of claim 47, wherein at least one subsequent rolling
step reduces the thickness of the composite assembly.
49. The method of claim 1, wherein applying pressure in step (c) is
accomplished by rolling or swaging.
50. The method of claim 49, wherein applying pressure is
accomplished by rolling.
51. The method of claim 50, wherein said rolling comprises a
plurality of rolling steps.
52. The method of claim 51, wherein the bond strength between the
wire and the metal base increases during the plurality of rolling
steps.
53. The method of claim 51, wherein said rolling comprises 2-10
rolling steps.
54. The method of claim 51, wherein said rolling comprises 3-6
rolling steps.
55. The method of claim 51, wherein at least a first rolling step
consolidates the composite assembly and constrains lateral
spread.
56. The method of claim 55, wherein at least one subsequent rolling
step reduces the thickness of the composite assembly.
57. The method of claim 1, wherein the step of providing a metal
base in step (a) comprises providing a metal base having two or
more depressions on at least one of said first and second opposing
surfaces.
58. The method of claim 57, wherein the step of providing a metal
base in step (a) comprises providing at least one depression
located in the center of the first opposing surface of the metal
base.
59. The method of claim 57, wherein the step of providing a metal
base in step (a) comprises providing at least one depression offset
from the center of the first opposing surface of the metal
base.
60. The method of claim 57, wherein applying pressure in step (c)
is accomplished by rolling or swaging.
61. The method of claim 60, wherein applying pressure is
accomplished by rolling.
62. The method of claim 61, wherein said rolling comprises a
plurality of rolling steps.
63. The method of claim 62, wherein the bond strength between the
wire and the metal base increases during the plurality of rolling
steps.
64. The method of claim 62, wherein said rolling comprises 2-10
rolling steps.
65. The method of claim 62, wherein said rolling comprises 3-6
rolling steps.
66. The method of claim 62, wherein at least a first rolling step
consolidates the composite assembly and constrains lateral
spread.
67. The method of claim 66, wherein at least one subsequent rolling
step reduces the thickness of the composite assembly.
68. A method of making a composite article having two dissimilar
metals, comprising: (a) providing a metal base comprised of a first
metal and having first and second opposing surfaces; (b)
positioning at least one wire comprised of a second metal at a
location on at least one of said first and second surfaces, wherein
the second metal comprises a cutting tool grade steel and is harder
than the first metal; (c) restricting the lateral movement of the
wire relative to its location on said surface to form a composite
assembly; and (d) heating the composite assembly under pressure to
urge the adjacent surfaces of the at least one wire and the metal
base together to form a bonded article and to reduce the thickness
of the metal base at the base/wire interface, wherein at least a
first rolling step consolidates the composite assembly and
maintains a lateral bonding pressure on the composite assembly.
69. The method of claim 68, wherein the step (c) of restricting the
lateral movement of the wire relative to its position on the metal
base comprises providing at least one longitudinally-positioned
depression in at least one of said first and second surfaces for
receiving said wire.
70. The method of claim 68, wherein the composite assembly is
pressed by rolling the composite assembly through a roll having a
groove in the roll surface in the direction of rolling, wherein the
wire is engaged in the groove and the pressure of the roll on the
wire and the metal base restricts lateral movement.
71. The method of claim 68, wherein at least one subsequent rolling
step reduces the thickness of the composite assembly.
72. The method of claim 68, wherein the step of heating the
composite assembly under pressure in step (d) comprises thinning
the metal base to the extent that a transverse cross-section of at
least a portion of the bonded article includes substantially no
first metal.
73. The method of claim 68, wherein the step of providing a metal
base comprises providing the first metal selected from the group
consisting of hot or cold rolled metal or metal alloys that are
spring-like.
74. The method of claim 68, wherein the second metal is selected
from the group consisting of high speed steels.
75. The method of claim 68 comprising forming a metallurgical bond
between the first and second metals.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of and claims the benefit
of priority under 35 U.S.C. .sctn. 120 of U.S. patent application
Ser. No. 10/207,409, now U.S. Pat. No. 7,373,857, filed on Jul. 29,
2002, entitled "Composite Metal Article and Method of Making",
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to metal articles made from
dissimilar metals. It also relates to improved methods of making
saw blades, and in particular, composite saw blades.
[0004] 2. Description of Related Art
[0005] Saw bands and saw blades must have high dimensional
stability of their cutting edges as well as high wear resistance.
They should also be able to withstand the high loading produced by
compressive, flexural and shearing forces, even under the
temperatures that result from the friction between the saw blade
and the material being sawn. Since it is difficult to combine the
properties mentioned above in a single material, saw blade nowadays
usually comprise a relatively tough metal base with high bending
fatigue strength and a cutting-edge band of a high-speed steel that
is less tough but highly wear resistant. The cutting-edge band is
of such a width that at least the teeth tips of the saw band or
blade, or even the cutting teeth as a whole, can be cut out from
it.
[0006] Composite saw blades, that is, saw blades made up of two or
more dissimilar materials, have been prepared by welding a thin
strip of cutting tool steel to an edge of a flexible alloy steel
backer. A common welding technique is electron beam welding;
however, the resulting weld, an alloy of the two metals and a
heat-affected area adjacent to it, is materially weakened. In
preparation for welding, and in particular for electron beam
welding, the metal backer and the thin strip of cutting tool steel
are rolled and annealed repeatedly to attain the desired dimensions
for welding. When welding dimensions are achieved, both the metal
backer and the strip still needs to be further conditioned to
obtain sharp, square edges at the site of welding. This process can
be very time consuming and costly.
[0007] Composite metal articles also have been prepared by casting
molten cutting tool steel against a supporting metal strip. The
molten cutting tool steel is fed into a space adjacent to the
supporting metal strip, where it bonds.
[0008] Solid phase edge bonding has been used for side-by-side
joining of metal strips by application of heat and pressure under a
reducing atmosphere. Solid phase bonding is accomplished by heating
the metal strips under sufficient pressure to form a metallurgical
bond. Although solid state bonding can produce a metallurgical bond
without deleterious effect to neighboring metal area, solid state
edge bonding does not generate sufficient new bonding surfaces,
heat and pressure to form a strong bond, and the joined strips
often do not survive subsequent processing.
[0009] Hot rolling of metals is known, and the hot rolling of steel
ingots has been in common practice for many years. Hot rolling is
usually carried out at temperatures around 2000.degree. F., and the
hot rolled steel typically is cold-rolled to its final dimensions.
It is often necessary when rolling high speed steel to anneal the
steel after each 10% to 30% cold worked reduction due to damage,
i.e., work hardening, resulting from cold working. Thus, cold
working requires additional time-consuming and costly processing
steps.
[0010] Hot bonding has been used to prepare composite metal
articles such as copper clad steel by heating a steel core and two
copper strips to hot rolling temperatures using electric resistance
heating. The three components are introduced into a chamber with a
reducing atmosphere and are then passed directly into a roll, where
pressure and heat bond the materials. As with hot rolling, it is
most often necessary to cold work the article to its final
dimensions.
[0011] Thus, improved methods for providing composite articles
having high bond strength between different metals are desired.
[0012] There remains a need for efficient manufacture of composite
metal articles.
[0013] There remains a further need for composite metal articles
having a strong bond between the component metals with minimal
material damage to the bonding region.
[0014] These and other limitations of the prior art are addressed
in the following invention.
BRIEF SUMMARY OF THE INVENTION
[0015] The present invention provides a composite metal article
that exhibits superior bonding between the dissimilar metals. The
composite article is capable of being further processed into saw
blades or other useful articles. A saw blade with superior cutting
and wear-resistant properties is provided.
[0016] The present invention also provides a simple and effective
method for forming a composite metal article. According to one
aspect of the invention, a method of making a composite metal
article from two dissimilar metals includes providing a metal base
comprised of a first metal and having first and second opposing
surfaces, said base having a least one longitudinally-positioned
depression in at least one of said first and second opposing
surfaces for receiving a wire; introducing an elongated metal
element comprised of a second metal into said at least one first
and second depressions of the metal base to form a composite
assembly; and heating the composite assembly under pressure to urge
the adjacent surfaces of the second metal elements and the
depressions together to form a bonded article.
[0017] In one or more embodiments, the metal base is a sheet or
strip. A sheet or strip has its conventional meaning and includes
one dimension, e.g., thickness, that is significantly smaller than
the other two dimensions, e.g., length and width. Exemplary
dimensions include an aspect ratio (width:thickness) of greater
than about 5.
[0018] In one or more embodiments, the metal base is a metal bar.
Metal bar has its conventional meaning and includes one dimension,
e.g., thickness, that is smaller than the other two dimensions,
e.g., length and width; however, the aspect ratio (width:thickness)
is not as great, e.g., 1:1 to about 4:1.
[0019] As used herein "transverse direction" is considered to be
the direction perpendicular to the plane of the base, or in the
direction of the applied pressure. The transverse direction
typically is across the thickness of the article.
[0020] In one aspect of the invention, a method of making a
composite metal article from two dissimilar metals includes
providing a metal base comprised of a first metal and having first
and second opposing surfaces, said base having at least one
longitudinal depression in at least one of said first and second
opposing surfaces for receiving a wire; introducing a wire
comprised of a second metal into said at least one depression of
the metal base to form a composite assembly; and heating the
composite assembly under pressure to urge the adjacent surfaces of
the second metal elements and the depressions together to form a
bonded article.
[0021] In another aspect of the invention, a method of making a
composite metal article from two dissimilar metals includes
providing a metal base comprised of a first metal and having first
and second opposing surfaces, positioning at least one wire
comprised of a second metal at a location on at least one of said
first and second surfaces; restricting the lateral movement of the
wire relative to its location on said surface to form a composite
assembly; and heating the composite assembly under pressure to urge
the adjacent surfaces of the at least one wire and the metal
together to form a bonded article.
[0022] In still another aspect of the invention, a method of making
a composite wire includes providing a metal bar comprised of a
first metal and having first and second opposing surfaces, said
base having a least one longitudinal depression in at least one of
said first and second opposing surfaces for receiving a wire;
introducing a wire comprised of a second metal into said at least
one depression of the metal base to form a composite assembly; and
heating the composite assembly under pressure to urge the adjacent
surfaces of the second metal elements and the depressions together
to form a bonded article.
[0023] In another aspect of the invention, a composite metal
article includes a base comprised of a first metal and having first
and second opposing surfaces; and at least one elongated member
comprised of a second metal, said at least one elongated member
embedded in at least one of said first and second opposing surfaces
and positioned along the length of the base, wherein the surface of
the base containing the embedded elongated member and the opposing
surface form planar surfaces, and wherein the base and the
embedded, elongated member form a metallurgical bond along their
interface.
[0024] In another aspect of the invention, a composite metal
cutting tool includes a base comprised of a first metal and having
a first thickness at a first edge and having a tapered region on
the opposing edge of the base that tapers from said first thickness
to a second, smaller thickness; and at least one edge member
located adjacent to the tapered edge region of the base, the edge
member comprised of a second metal and forming a metallurgical bond
with a surface of the tapered region of the meal base, such that
the thickness of the edge member and the tapered region of the
metal base is the same as the first thickness of the metal
base.
[0025] In still another aspect of the invention, a turks' head
having improved restraint on lateral spread includes a first pair
of horizontal rolls; and a second pair of vertical rolls located at
the edges of the horizontal rolls, wherein the rotational axis of
the vertical rolls is offset upstream of the rotational axis of the
horizontal rolls, said offset being within the arc of contact of
the horizontal roll with a material to be processed.
[0026] In yet another aspect of the invention, an apparatus of
making a composite metal article includes:
[0027] means for introducing a metal base into a first controlled
atmosphere;
[0028] means for introducing first and second elements into a first
controlled atmosphere and for positioning the first and second
elements adjacent to the metal base at a location where bonding is
to occur;
[0029] means for heating the metal base and first and second
wires;
[0030] at least one roll pair for applying pressure to the metal
base and two wires; and
[0031] means for monitoring and controlling tension.
[0032] As used here and throughout the specification, the term
"about" refers to .+-.10% of the stated value.
BRIEF DESCRIPTION OF THE DRAWING
[0033] Various objects, features, and advantages of the present
invention can be more fully appreciated with reference to the
following detailed description of the invention when considered in
connection with the following figures, in which like reference
numerals identify like elements. The following drawings are for the
purpose of illustration only and are not intended to be limiting of
the invention, the scope of which is set forth in the claims that
follow.
[0034] FIG. 1A is a side view, FIG. 1B is a perspective,
cross-sectional view across section 1B-1B', and FIG. 1C is a
cross-sectional view before slitting, illustrating the features of
a composite article according to one or more embodiments of the
invention.
[0035] FIG. 2 is a cross-sectional view before slitting (2A), after
slitting(2B), and after sharpening to a knife edge of a composite
article (2C) according to one or more embodiments of the
invention.
[0036] FIG. 3A is a cross-sectional view of a conventional welded
article and 3B is a cross-sectional view of a bonded article
according to one or more embodiments of the present invention
showing the shear line of the bond.
[0037] FIG. 4 is a cross-sectional illustration of one or more
embodiments of the composite metal article of the invention in
which the edge member has a plurality of alternating layers of hard
cutting tool metal and a more flexible, supporting metal.
[0038] FIG. 5 illustrate a cutting tool according to one or more
embodiments of the present invention.
[0039] FIG. 6 is an illustration of the assembled composite of two
dissimilar metals according to one or more embodiments of the
invention (A) prior to bonding; (B) after at least one
consolidation step (arrows indicate applied pressure); and (C)
after additional consolidation steps, and (D) an enlargement of the
bonding region.
[0040] FIGS. 7A-7D are cross-sectional illustrations of various
embodiments of the metal base and depressions used in one or more
embodiments of the present invention.
[0041] FIGS. 8A-8C is an illustration of the assembled composite of
two dissimilar metals according to one or more embodiments of the
invention (A) prior to bonding; (B) after at least one
consolidation step; and (C) after additional consolidation
steps.
[0042] FIG. 9 illustrates composite assembly according to one or
more embodiments of the present invention.
[0043] FIGS. 10A through 10D illustrate the preparation and use of
a composite metal, wire according to one or more embodiments of the
present invention.
[0044] FIG. 11A is an illustration of one embodiment of the present
invention in which the bonding region in the metal base is offset
from center, and 11B is a method of making a composite article in
which the edge members are offset from center according to one or
more embodiments of the invention.
[0045] FIG. 12 illustrates an embodiment of the present invention
for constraining lateral spread of the composite article using
matched male/female rolls.
[0046] FIG. 13 illustrates another embodiment of the present
invention for constraining lateral spread of the composite article
using an offset turks head.
[0047] FIG. 14 illustrates a multi-stand mill for fabrication of
the composite articles of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0048] The present invention provides a composite metal article
that exhibits superior bonding between the dissimilar metals. The
composite metal article is formed between at least two dissimilar
metals. As used herein, it is understood that the term "metals"
includes metal alloys. The composite metal article is comprised of
a metal base and one or more other metal elements that form a
strong bond with the metal base. The bond is formed without
deleteriously altering the chemical, metallurgical and/or
mechanical properties of article adjacent to the bond.
[0049] In one or more embodiments, a metal edge member is bonded on
both sides of a metal base along one side of the body of the base.
An exemplary composite metal article according to one or more
embodiments of the invention is shown in FIGS. 1A and 1B. The
article 100 includes a base 110 having a tapered edge 125 comprised
of a first metal and an edge member 128 located adjacent to the
tapered edge 125 of the base 110. FIG. 1A also shows an example of
a finished product, e.g., a saw blade, having cutting teeth 140 in
the edge member 128 of the composite article. As shown in the
perspective view in FIG. 1B, the metal base 110 includes a tapered
section 125 that is in contact with edge members 128, 128' on
opposing surfaces 129, 129' of the thinned, tapered section 125.
Edge members are tapered complementary to the taper of section 125,
so that the article surface is flat. The taper may be linear or
curved, or a more complex geometry resulting from material flow
during fabrication. The edge members 128, 128' and the thinned,
tapered section 125 of the base 110 form a strong, i.e.,
metallurgical, bond at the opposing surfaces. As is shown in FIG.
1C, the composite article is prepared from an intermediate
composite sheet 180 including two opposing elongated metal elements
126, 126' embedded in and bonded to the metal base 110. the
elongated metal elements 126, 126' are trench-like strips that run
the length of the composite sheet 180. The composite sheet is slit
along line 130 in FIG. 1C to obtain the article shown in FIG. 1B.
The composite sheet optionally is also slit along selvage lines 140
to provide a straight even edge to the final article.
[0050] Due to the highly effective metallurgical bonding of the two
dissimilar materials at the atomic level, the interface is very
clean with a discreet bond interface; however, there is no
embrittled alloys formed in the bonding zone, as is typical of
electron beam welded articles. The thickness of the thinned section
125 can vary according to the contemplated uses of the article of
the invention, and can range from about 70% to an insignificant
amount of the total thickness, as measured at the exposed surface
160 of the slit article or as measured at the narrowest point 150
between opposing elements (or adjacent to the metal element in
those embodiments having only one elongated metal element). In one
or more embodiments, the base metal thickness at point 150 or 160
can range to about 30%, or is about 5-15% of the total thickness.
The edge members 128, 128' (or the elongated metal elements 126,
126') may have substantially equal thickness on either side of the
tapered base section, however, it is recognized that manufacturing
process may cause the edge members 128, 128' (or the elongated
metal elements 126, 126') to vary somewhat in thickness. In one or
more embodiments, the edge members 128, 128' (or the elongated
metal elements 126, 126') may be of unequal shape, size and
thickness. Improved cutting properties have been observed in blades
prepared from the composite metal article of the invention.
[0051] In one or more embodiments, a composite metal sheet 200
includes an elongated metal element 210 embedded in and bonded to
one side of a metal base 220, as is shown in FIG. 2A. The composite
metal sheet 200 is slit at line 240 of FIG. 2A to give a composite
article 245 that is illustrated in FIG. 2B. The composite article
245 includes an edge member 215 bonded to a thinned, tapered
section 218 of the base 220 along the length of one side of the
base. The taper of the tapered section 218 is complementary to the
edge member 215 so that the surface 225 of the article 245 is flat.
As in FIG. 1A above, cutting teeth may be cut into a cutting edge
250 of the article. Alternatively, the edge may be sharpened to
form a knife edge 270, as is shown in FIG. 2C. Such edges are used
in band saws and/or in the manufacture of knives. The thickness of
the thinned, tapered section 218 or 260 can range from about 1 to
70%, or about 1 to 30% of the total thickness of the article. The
tapered region 218 or 260 of the metal base can be exceedingly thin
at its narrowest point, to the extent that it is not readily
observable (with the naked eye) or detectable only under
magnification.
[0052] In one or more embodiments of the present invention, the
first metal is tougher, e.g., has a higher hardness, than the
second metal. In one or more embodiments, the base is a metal
having desirable properties of mechanical and thermal stability,
for example, under the conditions typically encountered in sawing
or cutting operations. In general, the metal base can be any hot or
cold rolled metal or metal alloy that is tough and spring-like. The
metal base exhibits flexibility, and metals that exhibit
flexibility, e.g., spring metals, can be used in the present
invention.
[0053] In one or more embodiments of the invention, the second
metal used as the cutting edge is harder or more wear-resistant
than the first metal. In one or more embodiments, the edge member
is a wear-resistant metal; for example, the edge member is made
from a metal capable of withstanding the abrasive conditions
typically encountered by the cutting edge under sawing or cutting
operations. The edge member metal can be one or more high speed
steels, including powdered metals. By way of example only, high
speed steels include Matrix II, M2, M42, M51, M3 Type 1, M3 Type 2,
and the like.
[0054] A feature of the present invention is that the article is
not limited to any specific metal or metal alloy for use in either
the metal base or the edge metal. Because bonding relies on the
diffusion of metal across a dramatically increasing interface,
almost any combination of metals can be used in the practice of the
present invention. This versatility is in distinct contrast to
conventional welding operations used in the fabrication of cutting
tools, which often require specific alloy compositions for
successful welding.
[0055] More complex articles are contemplated in accordance with
the present invention. In one or more embodiments of the invention,
a cutting edge 400 of a composite metal article 410 as shown in
FIG. 4 includes a plurality of alternating layers of hard cutting
tool metal 420 and a more flexible, supporting metal 430. The
innermost section 440 represents the thinned, tapered section of
the metal base. The metal used for the flexible, supporting metal
sections 430 can be the same as or different from the metal of the
metal base 440. The metal components of the cutting edge are
metallurgically bonded at shared surfaces. The thickness of the
flexible, supporting metal sections 430 can be the same as or
different from the thickness of the innermost section 440. For
example, FIG. 4 illustrates a composite metal article having three
sections 430, 440, 430' of flexible, supporting metal of varying
thicknesses. The number, thickness and location of the different
metal regions in the edge member are selected to provide a desired
property in the article.
[0056] The base and edge members of the composite article form a
metallurgical bond using the method of the present invention as
described herein below. The bond results from the atomic
interaction and rearrangement at the interface of the two metals at
moderate temperatures, i.e., below the temperature of any
metallurgical transformation (T.sub.m) of either metal. Unlike more
conventional joining methods, such as electron beam welding or
laser welding techniques, there is no significant area near the
joint that is materially affected, i.e., weakened, by the joining
process. The strength of the bond also arises from the differences
in the shear line between a welded article and the bonded article
of the present invention. A shear line 310 in conventionally welded
article 320 is shown in FIG. 3; and the shear lines 330 of the
composite article 340 according to one or more embodiments of the
present invention are shown in FIG. 3B. The length (and related
area) of the shear line is much larger for the inventive article
shown in FIG. 3B than for the conventional article of FIG. 3A.
Thus, even if the bond strengths were identical, the composite
article of the present invention would be more durable, long
lasting and more resistant to shear failure.
[0057] The resultant metallurgical bond strength varies according
to the materials and methods used in its manufacture; however, the
bond is at least strong enough to survive subsequent post-bonding
fabrication steps. In the case of saw blade fabrication, the
resultant metallurgical bond strength between the base metal and
the edge metal is strong enough to withstand slitting, cutting and
tooth setting, which are typical post-bonding fabrication steps.
After fabrication, the resultant article is typically subjected to
a heat treatment to harden the article.
[0058] The composite metal article of the invention is useful in
the fabrication of cutting tools, i.e., blades. Any variation of a
cutting tool is contemplated according to the present invention. A
cutting edge of any geometry can be machined into the edge member
of the composite article. In one or more embodiments of the present
invention, the blade is a toothed blade, e.g., a saw blade such as
hand and powered hacksaw, hole saw, jigsaw, reciprocating saw and
band saw blades. In one or more embodiments, the blade is a
toothless blade, e.g., a knife. By way of example only, a blade can
be welded, e.g., butt-welded, to form a band saw blade, or the
surface can be machined cut to form a smooth, toothless saw edge or
a knife edge
[0059] Cutting teeth are machined into the cutting edge using
conventional processes. The teeth can be of any geometry and
orientation suitable for a particular cutting application. The
cutting teeth can be arranged in any way desired along the cutting
surface. The teeth can be in or out of plane from the base, as is
needed by a particular cutting application. In short, one is free
to design the cutting tool as is most appropriate for a particular
cutting application.
[0060] In one or more embodiments of the present invention, the
cutting teeth are formed from a combination of a hard cutting tool
metal and a softer, supporting metal. The cutting edge presented to
a surface to be cut includes alternating regions of hard cutting
tool metal and softer metal. In one or more embodiments of the
invention, the cutting edge is provided in the form of a composite
metal. The cutting edge includes alternating regions or sections of
hard and soft metal that have been solid state bonded to each other
and include the edge members and tapered regions of the composite
metal article shown in FIGS. 1, 2 and 4.
[0061] In one or more embodiments, the cutting tool is a hybrid
article including a composite metal cutting strip that is prepared
in a separate step and that is welded, after fabrication, to a
metal base. FIG. 5 shows a hybrid saw blade 1245 using a
conventional base 1250. A composite metal cutting edge 1260
includes a solid state bonded composite of alternating layers of
hard cutting tool steel 1265 and softer supporting metal 1270. The
composite metal cutting edge is formed into a strip, which is then
welded to the base using conventional welding techniques. Cutting
teeth are then cut into the composite metal cutting edge so that
the alternating layers of cutting tool steel and soft metal
provides the cutting edges of the present invention
[0062] The composite metal article of the present invention is
prepared by heating an assembly of dissimilar metal components
under pressure to form a bonded article, a process known as solid
phase bonding. The composite assembly includes a metal base, such
as a sheet or strip, having at least one depression or groove
positioned longitudinally on one or both sides of the metal base
that is capable of receiving an elongated metal element. The term
"wire" or "insert wire" may be used as an alternative for
"elongated metal element" without loss of any scope afforded the
latter term. The wire can be of any shape, and is selected based
upon any number of factors, including raw material availability,
ease of manufacture, and the desire to complement the shape of the
longitudinal depression of the metal base. An exemplary composite
assembly 500 including a metal base 510 and elongated elements 520,
525 positioned in depressions 530, 535, respectively, of the metal
base 510 is shown in cross-section in FIG. 6A. It is contemplated
that the wire insert can project above the plane of the metal
sheet. In one or more embodiments, the metal base 510 is made from
a first metal that is different from the metal used as the wire
inserts 520, 525. Insert wires 520, 525 need not be made from the
same metal. The components are cleaned using conventional
detergents and scrubbing techniques prior to assembly.
[0063] The grooves and related elongated elements can be of any
shape or geometry. In one or more embodiments, the elongate element
is a rod, bar, wire. The elongated element or wire can have any
cross-sectional geometry; for example, a cross-section that is
round, oval, polygonal, square, rectangular or rhomboid, and the
like, is contemplated. The elongated element can be used in the
size and shape provided by the manufacturer. Alternatively, the
wire can be processed to a particular size and shape by any
conventional method, including by not limited to, drawing, turks
head, or wire extrusion. The wire may be reduced from an initial
dimension by warm or hot rolling (below T.sub.m).
[0064] The elongated elements may be, but are not required to be,
complementary to the groove in the metal base. A large amount of
variability is possible in forming wire inserts-metal base
combinations, so long as the shape of the depression is adapted to
receive the wire insert. In one or more embodiments, the
combination is selected to "lock" the wire into the groove of the
metal base. This is typically accomplished by establishing at least
two points of contact between the wire insert and the groove. Thus,
by way of example only, a round wire in a v-groove or a trapezoidal
wire in a round groove provides sufficient contact. In one or more
embodiments of the present invention, the wire insert and the
groove can be of complementary shapes so that elongated element
matches the shape of the groove or depression of the metal
base.
[0065] The composite assembly is then heated under pressure to
bring the metal base and the elongated elements into intimate
contact and to form a metallurgical bond between the component
metals. In one or more embodiments, the composite assembly is first
heated to a temperature that is above room temperature and below
the temperature of any metallurgical transformation (T.sub.m) of
any of the metals of the composite assembly and then passed through
a pair of rolls (a "mill roll") to exert bonding pressure and to
reduce the article thickness.
[0066] Although the actual temperatures used will vary depending
upon the materials and pressing procedure used, temperatures can
range from about 800 to about 1600.degree. F., or in some
embodiments from about 1000 to about 1550.degree. F. Heating can be
accomplished using any conventional method. By way of example, the
composite assembly is heated using inductive or electrical
resistance heating. In one or more embodiments, the heat is
supplied by a form of radiation, for example, laser radiation.
[0067] Similarly, the actual pressures used in the practice of the
method of the invention will vary greatly depending upon the
materials and pressing procedure used. The pressure can be
generated using any conventional method. By way of example,
pressure is generated using a rolling mill or a turks head.
Pressure is a function of many variables including, but not limited
to, roll diameter, material deformation resistance (hardness),
metal thickness, and the coefficient of friction between the roll
and the metal being rolled, and the forces generated in rolling are
well known in the industry. In one or more embodiments of the
present invention, rolling occurs without lubrication of the rolls,
which increases the rolling pressure. In one or more embodiments,
the addition of a hard insert wire, and in particular the addition
of two wires stacked one on top of the other above and below the
metal base, causes higher pressure at the point of contact--the
specific location where high pressures are desired to improve
bonding. The additional thickness locally due to the presence of
the elongated element provides additional pressure for improved
bonding during the solid phase bonding operation.
[0068] The metal base has one or more grooves or depressions
longitudinally-positioned on one or both sides of the metal base.
FIG. 7 shows exemplary embodiments of the metal sheet. FIG. 7A is a
cross-sectional view of a metal base 600 having a depression 610 on
the top and bottom surfaces that is shown, by way of example, as a
rectangular groove. This metal base is referred to as a "two-up"
sheet, as slitting the base through the center of the groove will
result in two product articles. FIGS. 7C and 7D are shown with
grooves having other profiles, for example, a triangular 620
profile or rounded 630 profile. Note for example that FIG. 7C has a
groove in only one side of the metal base. This configuration is
used when a single elongated element is bonded, such as is
discussed with reference to FIG. 2. In one or more embodiments, a
metal sheet 640 includes two or more depressions 650, as is shown
in FIG. 7B. Each depression is capable of receiving an elongated
element, such as a wire, and the metal sheet 640 can be divided
into several composite articles after bonding by appropriate
slitting of the bonded article through the center of the groove and
the area between the grooves as indicated by the dashed lines 660
in FIG. 7B. In one more embodiments, the rolled article can be a
1-up, 2-up, 4-up, 6-up, 8-up sheet and the like. While there is no
limit to the number and the width of articles that can be obtained
using the method of the present invention, the wider the material
to be rolled, the more challenging the process.
[0069] FIG. 6B is an illustration of the article 545 at an
intermediate point during the heating and rolling process. The
insert wires 520, 525 are pressed against and into the metal base.
In one or more embodiments, the metal base is also being reduced in
thickness. The greater the thickness reduction of the metal base
(expressed as % reduction), the greater the forces experienced at
the interface between the metal components. Thus, the wire size and
shape and metal sheet thickness and groove size and shape relate to
the bonding forces experienced by the composite assembly, and at
the point where the insert wire(s) is introduced into the base
groove, the large reduction forces favor stronger solid state
bonding.
[0070] FIG. 6C illustrates a final bonded article 558, in which the
pressure has forced the second metal of the wire insert into the
metal base and the article surface is substantially flat. The
contact area between the wire and the base has increased
considerably during the bonding process due to thickness reduction
and article elongation. In creased contact area provides a large
bonding interface and contributes to the high quality of the bond.
The metal base 510 has thinned considerably in a bonding area 548
so that only a thin strip 540 of the metal base is found between
the upper and lower regions 550, 555 arising from the former insert
wires. In one or more embodiments, the area can be sufficiently
thinned such that only a small amount of the metal base remains and
essentially the entire cross-section 560 is comprised of the second
metal from the insert wires, as shown in the enlarged bonding
region 570 in FIG. 6D.
[0071] Thus, in a few simple (and rapid) steps, the method of one
or more embodiments of the invention provides a bonded article of a
desired thickness. The starting materials can be thicker than those
used in conventional electron beam welding processes, yet final
thickness is achieved in fewer steps and less time, resulting in a
significant savings in cost and materials.
[0072] In one or more embodiments using insert wire above and below
the metal base, it is desired to keep the wires registered in
place. In instances where the wire can move laterally, the
resultant bonded sections of the wire insert can shift during
rolling so that the resultant bonded regions are offset from one
another. Use of a wire insert and groove geometry that forms a
multipoint contact is helpful in reducing lateral shift of the
bonded second metal region.
[0073] In one or more embodiments of the present invention, the
arrangement and geometry of the wire, metal base and rolls are
selected to reduce the relative movement of the wire and base. If
the wire shifts during processing, the resultant bonded metal
element may be out of position for subsequent processing, e.g.,
slitting. In particular for the case where a wire pair are
positioned above and below the metal base, it is desired to
maintain accurate position of the components of the composite
assembly. In one or more embodiments, the upper and lower
depressions are kept in close alignment to the desired
position.
[0074] In one or more embodiments of the present invention, the
roll, metal base, or both, includes a groove that engages the wire
insert to constrain the lateral movement of the insert wire. As is
shown in FIG. 6A, roll 575 has a groove 580 that accepts the insert
wire and holds it in position with respect to the roll. A lower
roll (not shown) with a similar notch engages the lower insert wire
in those embodiments that include one.
[0075] In one or more embodiments, the wire 1300 is engaged in a
groove 1310 of a roll 1320 that runs in the rolling direction. When
there is a deep groove in the rolls (shown in FIG. 8A by way of
example as 1/2 d, where d is the wire diameter), no depression in a
metal base 1330 is required to fix the wire position. A first
rolling pass shown in FIG. 8B fixes the location of the wire by
embedding the wire into the metal base and, once fixed, a
subsequent pass (FIG. 8C) drives the fixed wire down into the metal
base, widening the wire into an embedded metal strip 1335 and
narrowing the thickness of the metal base at the bonding region
1340 in the process.
[0076] In one or more embodiments, the wire is engaged in the
depression of the metal base and no roll groove is employed to fix
the component positions. As shown in FIG. 9, when the wire 900 is
flat so that it nests deeply in depression 910 of the metal base
915, lateral movement is sufficiently constrained so that the roll
920 is not required to be grooved in order to fix the relative
positions of the wire and metal base.
[0077] The composite metal article of the invention can be further
processed to obtain the desired article. For example, in the
manufacture of saw blades, the composite article is divided into
two similar pieces by slitting the article through the center
region 548 or center region 570 of the article. See FIG. 6. In one
or more embodiments, the upper and lower bonded metal elements are
substantially symmetric and are stacked above and below each other
so that the composite metal article can be divided at about the
center point of the bonding region to provide two substantially
identical pieces. The slit piece from an article having a thinned
first metal center such as region 548 has an edge with the
structure shown in FIG. 1C.
[0078] In one or more embodiments, the elongated metal element used
as an insert wire also is a composite metal. FIG. 10A is a
perspective drawing of a composite elongated metal element (wire)
700 of the present invention. The element 700 includes a metal 710,
for example one that is similar to or the same as the first metal
used for the metal sheet 755, and a dissimilar metal 720. In one or
more embodiment, metal 720 is harder than metal 710. The component
metals are arranged in alternating regions and the metal regions
are bonded at their interfaces. In one or more embodiments, the
harder metal 720 is located at an outer surface so that the harder
metal provides increased wear resistance to the composite.
[0079] FIG. 10C illustrates a composite assembly 750 using the
composite metal element 700 and a metal base 755. It is desired
that the composite wire is aligned in a plane of the metal base and
remains so aligned during consolidation and bonding. Proper
alignment includes positioning the composite wire in the metal base
so that the alternating layers of metals 710 and 720 are
substantially parallel with the plane of the metal base. In one or
more embodiments, the composite wire nests or fits snugly into a
groove 725 of the metal base 755 and/or into a groove of the
bonding roll (not shown). In one or more embodiments, the composite
wire is of a shape, e.g., trapezoidal and the like, that
discourages rotation of the composite wire within the groove. In
one or more embodiments, the bonding rolls and/or the metal base
includes a v-groove. In one or more embodiments, neither the
depression of the metal base nor the composite wire is round. The
heated components are assembled and pressed to form the bonded
article.
[0080] FIG. 10D illustrates the final composite metal article 560
after the heat and pressure treatment of the present invention. The
bonded region 765 includes alternating layers of metals 710 and 720
disposed in a bonding region 765 of the metal base. The
thus-obtained composite sheet is slit vertically through the
central section of the bonding region 765 to reveal an edge of
alternate layers of hard metal sections (720) and flexible
supporting metal (710, 755). An exemplary resultant article is
shown in FIG. 4.
[0081] FIG. 10B illustrates a method of assembly of the composite
wire. A conventional steel bar 730 is preshaped in a form, here a
barbell, that can accommodate round (or some other shape), wear
resistant steel wire 740, 740'. The bar includes depressions above
and below, which can be introduced by drawing turks head rolling or
conventional v-groove rolling of a conventional bar or round wire.
The three components are cleaned using conventional detergents and
scrubbing techniques, bonded and rolled to a final consolidated
dimension. Bonding of the wire can be accomplished using a hot
rolling process or according to the method of the present invention
or any other technique that serves to metallurgically bond the wire
components. Alternatively, the assembly can be processed in a turks
head process using a turks head having an inverted groove roll that
provides adequate pressure to bond the composite wire.
[0082] The final bonded articles can have varying thicknesses, for
example, ranging from about 0.020'' to about 0.100''. Articles
having small final thicknesses and/or relatively large percent
reduction (e.g., large increases in the area of interface) tend to
form very strong bonds. In instances where the final thickness is
relatively large, e.g., 0.065'' or greater, or where the percent
reduction in thickness is not very large, the bonding strength is
not as high. In other instances where the overall article is very
wide, one may not want to use rolling to attain the entire width as
flow properties can vary over the greater distances. In these (and
other) instances, a composite cutting edge can be welded to an edge
of the metal base using conventional welding techniques to provide
the cutting edge of the present invention. An example of such an
article has been previously described (FIG. 5).
[0083] A method of making a welded product having a composite metal
edge is now described with reference to FIG. 11A. A composite metal
wire 700 is prepared as described above with reference to FIG. 10.
The consolidated wire is bonded using heat and pressure and rolled
to rectangular cross section 1100, for example, by turks head
rolling or by alternating steps of vertical rolling and horizontal
rolling. Selvage edge 1110 optionally is cut from rectangular form
1100 to expose a surface 1125 having alternating regions of hard
metal 1120 and softer metal 1130 metals. The cut rectangular form
1100 is welded to a base 1140 at the side opposite the exposed
surface to form a welded composite metal article 1150. The metal of
the base and the soft metal of the composite edge are the same or
similar metals.
[0084] Similarly, the article can be of any width, and can for
example range from less than 1/4'' to 31/2'' or more. FIG. 11B
illustrates a method and article using offset bonding, e.g.,
bonding at a location off set from center and near the edge of the
article. In those instances where a large blade 1160, e.g., a
31/2'' blade is desired, it may not be convenient to bond a "2 up"
article. In such cases, the longitudinal depression 1170 can be
offset to one side of the metal base and a single width article ("1
up" article) is rolled. The edge is cut off at the selvage line
1180 to reveal the composite cutting edge, with the balance being
selvage, as is shown in FIG. 11B.
[0085] In one or more operations, solid phase bonding of the
dissimilar metals is accomplished using bonding rolls and/or turks
head rolls for the application of heat and/or pressure. In one or
more embodiments, bond rolling is carried out using a plurality of
bonding rolls or "stands." A stand is a component of a mill used
for the bonding operation. Each stand includes a pair of bonding
rolls that is independently motor driven and independent "screw
down" gear assembly used to adjust the vertical position of the
rolls for the application and release of pressure at the rolls and
control of material thickness. A mill includes a plurality of
independent rolling stands operating in tandem and in communication
with one another through "bridges" or enclosures that span between
the exit of one stand and the entrance of the next stand in order
to keep the materials being bonded in a controlled, typically
reducing, atmosphere. In one or more embodiments, the mill includes
two or more rolling stands, and can include 3 to 6 stands, or
more.
[0086] Many modifications and variations of the process are within
the scope of the invention. It is appreciated that a pressing
operation such as rolling will either elongate or widen the
composite article. In the present invention, there is an additional
cause for lateral spread due to the presence of additional material
(the elongated elements) which are being forced into the center of
the metal sheet directly over one another. Left unattended, the
lateral spread causes the center of the rolled form to fracture. In
one or more embodiments, the bonding cavity, i.e., the space
between the bonding rolls, have the ability to restrain lateral
spread. "Restraining lateral spread" as that term is used herein,
means that the lateral spread is substantially reduced or
eliminated (it is recognized that a small amount of lateral spread
will occur despite steps taken to prevent it), or that the material
is allowed to spread laterally to a predetermined width, at which
point the material is constrained from further spreading. The
materials being reduced in the bonding cavity are allowed to spread
forward and to the rear along the axis of the metal sheet or strip.
In addition to providing a product of uniform dimensions,
constraining lateral spread has been found to maintain bonding
pressures of the article to enhance the quality of the bond.
[0087] In one or more embodiments, lateral spread is restrained in
a rolling operation by employing a male 1000/female 1005 bonding
roll arrangement such as that shown in FIG. 12A, and having a
clearance area 1010 at the edges of the rolls. Under rolling
pressure, the metal base material attempts to flow up into the
large clearance area 1010. The spaces at the edges of the roll are
designed to permit the rolled base metal to flow (deform
plastically) partly up into the space provided. This upward flow is
limited by friction and flow ceases. In at least one or more
embodiments, the edges 1020 of the rolls are curved to facilitate
material flow. The clearance area can be angled, so that the
further the metal flows into the area, the narrower the metal path
becomes and the greater the friction restraining it. In one or more
embodiments, the rolls further include a notch 1040 on the roll
surface for receiving a portion of the composite assembly and
reducing the lateral movement of the assembled components in the
roll during the rolling operation. The notch assists in maintaining
the bonded elongated elements (derived from the insert wires)
registered in place, either as a specified location along the roll
and/or stacked over one another. In one or more embodiments, a
second rolling stand 1070 reverses the direction of clearance area,
as shown in FIG. 12B. In operation, the composite assembly is
rolled under heat and pressure at a first male/female rolling
stand, where the elongated element is engaged in the metal sheet
groove and lateral flow is restrained. The composite assembly is
rolled to a thinner dimension at a second stand for which the
direction of the clearance area is reversed and the second metal is
further embedded and flattened into the metal sheet. Subsequent
rolls do not require a male/female roll arrangement as the spread
no longer threatens to split the thin web of material and all
subsequent rolls 1080 are flat (with a small crown as is
conventional to accommodate over-rolling the edges).
[0088] In one or more embodiments, lateral spread is restrained
using an edge roll system, e.g., a turks head. A "turks head" is a
special configuration of a rolling mill, i.e., it is two mills set
up to roll in the same plane. A rolling mill becomes a turks head
when an additional roll pair is used whose rolling axis is
positioned at 90.degree. relative to the mill rolls rolling axis.
The turks head rolling axis is coplanar with the plane of
reduction. As the material passes through a bonding roll and
material is spread laterally to the sides of the roll, the turks
head rolls apply an opposing force to material at its edges. A
turks head is employed in the initial rolling stages, for example,
in the first two mill stands where significant lateral flow can
otherwise cause the base metal to split at the groove. While all
mill stands reduce the base (web) thickness to about the same
degree, a large percentage of thickness reduction occurs at or
around the insert wire in the initial stages when the wire is
embedded into the metal base.
[0089] For the purposes of this invention, it is desirable that the
side rolls do not produce a "flash" (a thin bead of metal that
flows between the mill rolls and turks head rolls). The present
invention has discovered that flashing can be avoided by locating
the side rolls slightly ahead (upstream) of the rolling axis of the
mill rolls. In one or more embodiments, the offset of the turks
head roll is within the arc of contact of the bonding roll with the
material to be rolled. The arc of contact 1400, as shown in FIG.
13A in elevation view, is the angle through which the bonding roll
1410 rotates from the point of initial contact 1430 of the roll
with the material 1420 to the narrowest point of contact 1440 (at
the nip). As soon as the material contacts the bonding roll, the
material experiences forces of increasingly greater magnitude, and
significant lateral spread can occur prior to the material passing
through the nip. Thus, positioning the turks head slightly ahead of
the nip prevents the lateral flow of the material. FIG. 13B is a
plan view of the offset turks head roll 1450 of the present
invention. The top mill roll is omitted for clarity, but dashed
lines 1455 indicate its location. The hatched area 1460 is the
contact area of the material and the mill rolls during the arc of
contact. The broken line 1465 denoted with "+" indicates the
typical increase in width observed for an unrestrained material.
Note that the material begins to widen shortly after contact with
the roll and well before the nip. To counteract this lateral flow,
side rolls 1470 are positioned upstream from the rolling axis of
the mill rolls (which coincides with the location of the nip 1440).
The side rolls provide an additional rolling force that opposes and
constrains the lateral flow of the material. Note that the mill
rolls are the same width as the target width in order for the side
rolls to be able to effectively constrain lateral flow.
[0090] In one or more embodiments of the present invention, the
offset is in the range of about 1/4'' to about 3/4''. As in the
case using male/female roll assemblies, the turks head roll is not
necessary once the thickness of the material is reduced by 2 or 3
passes. In one or more embodiments, the turks head roll is used in
the first, second and optionally, third stands.
[0091] In one or more embodiments, a turks head is employed to
limit the lateral spread to a predetermined value. In one or more
embodiments, the turks head can be allowed to spread or can be
located a distance from the edge of the mill roll. When the
material enters the mill roll, the material will spread a
predetermined amount up to the point where it meets the turks head.
In one or more embodiments, the metal base is narrower than the
mill roll width, and the turks head is positioned at the edge of
the mill roll (or may be located a distance from the edge of the
mill roll). Again, the material is able to spread laterally, but
only to a point at which it contacts the turks head roll.
Controlled lateral spread can result in the controlled thinning of
the base, particularly in the bonding region where the insert wires
and metal base are in contact. Controlled lateral spread can be
used to thin the metal base in the bonding region to the point that
is breaks or thins to a point that the base metal is effectively
absent.
[0092] An exemplary process for the manufacture of a composite
metal article according to one or more embodiments is
described.
[0093] The insert wire 1500 is shaped to the desired dimension and
cross-section, for example by cold or hot working. The shaped wire
is cleaned using standard metals cleaning procedures to remove
residual oils and oxides. Wires can be butt-welded into long
lengths to increase run times. In an exemplary process a 0.095''
round wire, e.g., M2, is rolled to 0.080'' by 0.105'' rhomboid
shape.
[0094] The metal base (6150) 1510 is initially obtained as
0.065-0.250'' thick and of a width necessary to provide the final
desired width and is turks head rolled to form a v-shaped (inverse
groove) depression on either side without changing the thickness
and with very little change in the width. The turks head pull
through technique is able to keep top and bottom grooves in
alignment within 0.002'' and in the center of the strip within
+/-0.005'' and also maintained the base thickness (although the
base may widen slightly).
[0095] The materials (insert wire 1500 and metal base 1510) are fed
off rolls and heated as they approach the mill stands using direct
current heating. With reference to FIG. 14, edge wire(s) and metal
base strip are paid off into (or through) a high potential contact
of a DC rectifier, e.g., 1520, 1530, respectively, for heating to
operating temperature (ca. 1250.degree. F.), and then are fed into
an entrance retort 1540 containing an oxide reducing atmosphere,
such as hydrogen. Oxidation/reduction cleaning is a known process
in which the material is heated in air to form a thin oxide layer
and then passed into an H.sub.2 containing retort for reduction.
Any organic residues or H.sub.2O remaining after scrubbing is also
removed. The edge wire is positioned above and below the base metal
strip as the components approach the first mill 1550. FIG. 14
illustrates a three-stand mill; however, composite metal article
has also been successfully prepared using a six-stand mill. The
number of mill stands used depends, in part, on the percent
reduction to be taken at each stand and the total final
thickness.
[0096] The mill stands include rolling mills that are surrounded by
a gas chamber 1555 that keeps the material in a reducing
atmosphere, although they can be exposed to air for brief periods.
A bridge retort 1560 spans between mill stands and maintains a
reducing atmosphere for the heated strip as it passes from mill to
mill. Exposure to atmosphere at these elevated temperatures would
otherwise result in surface oxidation. The mill rolls are made from
durable hard materials, such as high speed steed, e.g., H13, or
tungsten carbide. The mill rolls are selected to minimize sticking
of the rolled materials. The mill rolls are typically hollow; and
they can be air- or water-cooled. For example, they are shell
mill-type rolls that are supported on an arbor capable of being
water-cooled.
[0097] Each mill rectifier operates on its own circuit so that it
may be independently controlled. The temperature drop of the
material as it exits one mill stand and enters a subsequent one is
monitored and the rectifiers adjust heating (e.g. voltage) to
compensate for temperature drop. A hybrid heating system using
resistance and induction heating is also possible. In a hybrid
system, the first mill stand is set up as a conventional bonding
configuration with ground contact at the first stand. Re-heating
the materials between successive hot rolling stands is accomplished
with high frequency induction units. As the wire/base metal
assembly enters the first mill stand at target temperature, mill
load is increased to target mill load. A load cell at each stand
monitors mill load. As each mill stand equilibrates to the target
temperature and mill load, the subsequent mill rolls are
engaged.
[0098] Typically the first mill stand roll speed is
operator-controlled and subsequent roll speeds are set as a
function of its predecessor's speed. As material is reduced in
gauge, the percent reduction is proportional to the speed
differential of the rolls. The web tension of the material between
mill stands can be monitored using a tensiometer 1570 and mill
speeds can be adjusted as needed to control web tension; however,
many other conventional methods of monitoring speed and thickness
may be used. Tension control is accomplished using a roll over
which the hot strip passes at a shallow angle. An arrangement
transmits the force to a load cell. The load cell feeds back to a
controller, which monitors the tension and makes mill speed
adjustments accordingly.
[0099] The bonded article exits the mill stands as a continuous
bonded strip 1580 that is taken up at spool 1590. Slitting is done
in a separate operation.
[0100] Although various embodiments that incorporate the teachings
of the present invention have been shown and described in detail
herein, those skilled in the art can readily devise many other
varied embodiments that incorporate these teachings. All references
mentioned herein are incorporated by reference.
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