U.S. patent application number 14/104038 was filed with the patent office on 2014-04-10 for composite article with coolant channels and tool fabrication method.
This patent application is currently assigned to Kennametal lnc.. The applicant listed for this patent is Kennametal lnc.. Invention is credited to Prakash K. Mirchandani, Billy D. Swearengin, Michale E. Waller, Jeffrey L. Weigold.
Application Number | 20140097553 14/104038 |
Document ID | / |
Family ID | 37565711 |
Filed Date | 2014-04-10 |
United States Patent
Application |
20140097553 |
Kind Code |
A1 |
Mirchandani; Prakash K. ; et
al. |
April 10, 2014 |
COMPOSITE ARTICLE WITH COOLANT CHANNELS AND TOOL FABRICATION
METHOD
Abstract
Embodiments of the present invention include composite articles
comprising at least a first region and a second region and methods
of making such articles. The first region may comprise a first
composite material, wherein the first region comprises less than 5
wt. % cubic carbides by weight, and the second region may comprise
a second composite material, wherein the second composite material
differs from the first composite material in at least one
characteristic. The composite article may additionally comprise at
least one coolant channel. In certain embodiments, the first and
second composite material may individually comprise hard particles
in a binder, wherein the hard particles independently comprise at
least one of a carbide, a nitride, a boride, a silicide, an oxide,
and solid solutions thereof and the binder comprises at least one
metal selected from cobalt, nickel, iron and alloys thereof. In
specific embodiments, the first composite material and the second
composite material may individually comprise metal carbides in a
binder, such as a cemented carbide.
Inventors: |
Mirchandani; Prakash K.;
(Hampton Cove, AL) ; Waller; Michale E.;
(Huntsville, AL) ; Weigold; Jeffrey L.;
(Huntsville, AL) ; Swearengin; Billy D.; (New
Hope, AL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kennametal lnc. |
Latrobe |
PA |
US |
|
|
Assignee: |
Kennametal lnc.
Latrobe
PA
|
Family ID: |
37565711 |
Appl. No.: |
14/104038 |
Filed: |
December 12, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11167811 |
Jun 27, 2005 |
8637127 |
|
|
14104038 |
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Current U.S.
Class: |
264/171.1 |
Current CPC
Class: |
B22F 5/10 20130101; Y10T
428/1317 20150115; B22F 7/06 20130101; B22F 2998/00 20130101; B22F
2005/004 20130101; B21C 23/22 20130101; B29C 48/18 20190201; Y10T
407/1904 20150115; B22F 2998/00 20130101; B22F 2005/001 20130101;
B22F 2998/10 20130101; B22F 2998/10 20130101; Y10T 407/19 20150115;
B21C 25/02 20130101; Y10T 428/131 20150115; B22F 3/20 20130101;
B22F 7/06 20130101; B22F 5/106 20130101; B22F 3/04 20130101; Y10T
408/907 20150115 |
Class at
Publication: |
264/171.1 |
International
Class: |
B29C 47/06 20060101
B29C047/06 |
Claims
1. A method of forming an article, comprising: coextruding at least
two composite materials comprising metal carbides to form a green
compact.
2. The method of forming an article of claim 1, wherein the
coextruding at least two composite materials is performed through a
die.
3. The method of claim 2, wherein the die comprises means for
making internal channels in the green compact.
4. The method of claim 2, wherein the die comprises at least one
wire.
5. The method of claim 4, wherein the at least one wire forms an
internal channel within the green compact.
6. The method of claim 4, wherein the die comprises at least two
wires.
7. The method of claim 6, wherein the die comprises three
wires.
8. The method of claim 4, wherein at least one wire is a flexible
wire.
9. The method of claim 8, wherein the flexible wire comprises at
least one of nylon, a polymer coated metal wire, polyethylene, high
density polyethylene, polyester, polyvinyl chloride, polypropylene,
an aramid, Kevlar, polyetheretherketone, cotton, animal gut, hemp
and jute.
10. The method of claim 4, wherein the wire is an inflexible.
11. The method of claim 10, wherein the wire comprises a metal.
12. The method of claim 1, further comprising: loading a feed
chamber with at least two cemented carbide grades.
13. The method of claim 12, wherein at least one cemented carbide
grade is in extruded form.
14. The method of claim 13, wherein the extruded form is at least
one of a rod, bar, and a tube.
15. The method of claim 12, wherein loading the feed chamber
comprises loading at least one cemented carbide grade in a rod
shape and at least one cemented carbide in a tube shape.
16. The method of claim 13, wherein a plurality of cemented carbide
grades are loaded into the feed chamber in the shape of a tube.
17. The method of claim 12, further comprising: extruding a first
cemented carbide grade in the form of a tube.
18. The method of claim 17, further comprising: extruding a second
cemented carbide in the form of a rod.
19. The method of claim 18, wherein the cemented carbide in the
form of a rod is extruded directly into a feed chamber of a
coextruder.
20. The method of claim 1, wherein composite materials are cemented
carbides.
21. The method of claim 1, wherein the green compact comprises two
cemented carbide grades and the cemented carbide grades are
coaxially disposed.
22. The method of claim 1, wherein at the die includes a channel
die.
23. The method of claim 22, wherein the at least two cemented
carbide grades are coextruded through a die comprising internal
spiral serrations.
24. The method of claim 22, wherein the at least two cemented
carbides are coextruded through a rotating die.
25. The method of claim 2, wherein the green compact comprises at
least one channel.
26. The method of claim 2, wherein the green compact comprises two
helical channels.
27. A method of producing a rotary tool having a composite
structure, the method comprising: placing extruded first powder
metal into a first region of a void of a mold; placing a second
metallurgical powder metal into a second region of the void, the
extruded first powder metal differing from the second metallurgical
powder; compressing the mold to consolidate the extruded first
powder metal and the second powder metal to form a green compact;
and over-pressure sintering the green compact.
28. The method of claim 27, further comprising: removing material
from the green compact to provide at least one cutting edge.
29. The method of claim 28, wherein the mold is a dry-bag rubber
mold, and further wherein compressing the mold comprises
isostatically compressing the dry-bag rubber mold to form the green
compact.
30. The method of claim 28, wherein removing material from the
green compact comprises machining the compact to form at least one
helically oriented flute defining at least one helically oriented
cutting edge.
31. The method of claim 27, wherein the extruded first compost
powder comprises at least one channel.
32. The method of claim 31, wherein the extruded first powder metal
comprises at least two channels.
33. The method of claim 27, wherein both the first powder metal and
the second powder metal comprise a powdered binder and particles of
at least one carbide of an element selected from the group
consisting of group IVB, group VB and group VIB elements.
34. The method of claim 33, wherein the binders of the first powder
metal and the second powder metal each individually comprise at
least one metal selected from the group consisting of cobalt,
cobalt alloy, nickel, nickel alloy, iron and iron alloy.
35. The method of claim 27, wherein the first powder metal and the
second powder metal each individually comprise 2 to 40 weight
percent of the powdered binder and 60 to 98 weight percent of the
carbide particles.
36. The method of claim 27, wherein at least one of the first
powder metal and the second powder metal comprises tungsten carbide
particles having an average particle size of 0.3 to 10 .mu.m.
37. The method of claim 27, wherein over pressure sintering the
compact comprises heating the compact at a temperature of
1350.degree. C. to 1500.degree. C. under a pressure of 300-2000
psi.
38. The method of claim 27, wherein compressing the mold comprises
isostatically compressing the mold at a pressure of 5,000 to 50,000
psi.
39. The method of claim 27, wherein the green compact formed by
compressing the mold comprises: a first region comprising a first
cemented carbide material provided by consolidation of the first
metallurgical powder; and a second region comprising a second
cemented carbide material provided by consolidation of the second
metallurgical powder, the first region and the second region
differing with respect to at least one characteristic.
40. The method of claim 39, wherein the characteristic is at least
one selected from the group consisting of modulus of elasticity,
hardness, wear resistance, fracture toughness, tensile strength,
corrosion resistance, coefficient of thermal expansion, and
coefficient of thermal conductivity.
Description
CROSS-REFERENCE TO EARLIER APPLICATION
[0001] This patent application is a divisional patent application
to co-pending U.S. patent application Ser. No. 11/167,811 to
Mirchandani et al. filed Jun. 27, 2005, and under the Patent
Statute 35 USC .sctn.120, applicants hereby claim the benefit of
the priority date of such U.S. patent application Ser. No.
11/167,811 to Mirchandani et al. filed Jun. 27, 2005. Further,
applicants hereby incorporate by reference herein said U.S. patent
application Ser. No. 11/167,811 to Mirchandani et al. filed Jun.
27, 2005 in its entirety.
TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION
[0002] The present invention is generally directed to methods of
forming articles, such as tool blanks, having a composite
construction including regions of differing composition and/or
microstucture. The present invention is additionally directed to
rotary tools and tool blanks for rotary tools having a composite
construction and at least one coolant channel. The method of the
present invention finds general application in the production of
rotary tools and may be applied in, for example, the production of
cemented carbide rotary tools used in material removal operations
such as drilling, reaming, countersinking, counterboring, and end
milling.
DESCRIPTION OF THE INVENTION BACKGROUND
[0003] Cemented carbide rotary tools (i.e., tools driven to rotate)
are commonly employed in machining operations such as, for example,
drilling, reaming, countersinking, counterboring, end milling, and
tapping. Such tools are typically of a solid monolithic
construction. The manufacturing process for such tools may involve
consolidating metallurgical powder (comprised of particulate
ceramic and binder metal) to form a compact. The compact is then
sintered to form a cylindrical tool blank having a solid monolithic
construction. As used herein, monolithic construction means that
the tools are composed of a material, such as, for example, a
cemented carbide material, having substantially the same
characteristics at any working volume within the tool. Subsequent
to sintering, the tool blank is appropriately machined to form the
cutting edge and other features of the particular geometry of the
rotary tool. Rotary tools include, for example, drills, end mills,
reamers, and taps.
[0004] Rotary tools composed of cemented carbides are adapted to
many industrial applications, including the cutting and shaping of
materials of construction such as metals, wood, and plastics.
Cemented carbide tools are industrially important because of the
combination of tensile strength, wear resistance, and toughness
that is characteristic of these materials. Cemented carbides
materials comprise at least two phases: at least one hard ceramic
component and a softer matrix of metallic binder. The hard ceramic
component may be, for example, carbides of elements within groups
IVB through VIB of the periodic table. A common example is tungsten
carbide. The binder may be a metal or metal alloy, typically
cobalt, nickel, iron or alloys of these metals. The binder
"cements" the ceramic component within a matrix interconnected in
three dimensions. Cemented carbides may be fabricated by
consolidating a metallurgical powder blend of at least one powdered
ceramic component and at least one powdered binder.
[0005] The physical and chemical properties of cemented carbide
materials depend in part on the individual components of the
metallurgical powders used to produce the material. The properties
of the cemented carbide materials are determined by, for example,
the chemical composition of the ceramic component, the particle
size of the ceramic component, the chemical composition of the
binder, and the ratio of binder to ceramic component. By varying
the components of the metallurgical powder, rotary tools such as
drills and end mills can be produced with unique properties matched
to specific applications.
[0006] Monolithic rotary tools may additionally comprise coolant
channels extending through its body and shank to permit the flow of
a coolant, such as oil or water, to the cutting surfaces of the
rotary tool. The coolant may enter the channel at the shank end and
exit at the drill point. The coolant cools the rotary tool and work
piece and assists in ejecting chips and dirt from the hole. The use
of coolant during machining operations allows for the use of higher
cutting speeds of the rotary tool and faster feed rates, in
addition to extending tool life. Rotary tools with coolant channels
are especially suited for drilling deep holes in hard
materials.
[0007] However, the monolithic construction of rotary tools
inherently limits their performance and range of applications. As
an example, FIG. 1 depicts side and end views of a twist drill 10
having a typical design used for creating and finishing holes in
construction materials such as wood, metals, and plastics. The
twist drill 10 includes a chisel edge 11, which makes the initial
cut into the workpiece. The cutting tip 14 of the drill 10 follows
the chisel edge 11 and removes most of the material as the hole is
being drilled. The outer periphery 16 of the cutting tip 14
finishes the hole. During the cutting process, cutting speeds vary
significantly from the center of the drill to the drill's outer
periphery. This phenomenon is shown in FIG. 2, which graphically
compares cutting speeds at an inner (D1), outer (D3), and
intermediate (D2) diameter on the cutting tip of a typical twist
drill. In FIG. 2(b), the outer diameter (D3) is 1.00 inch and
diameters D1 and D2 are 0.25 and 0.50 inch, respectively. FIG. 2(a)
shows the cutting speeds at the three different diameters when the
twist drill operates at 200 revolutions per minute. As illustrated
in FIGS. 2(a) and (b), the cutting speeds measured at various
points on the cutting edges of rotary tools will increase with the
distance from the axis of rotation of the tools.
[0008] Because of these variations in cutting speed, drills and
other rotary tools having a monolithic construction will not
experience uniform wear and/or chipping and cracking of the tool's
cutting edges at different points ranging from the center to the
outside edge of the tool's cutting surface. Also, in drilling
casehardened materials, the chisel edge is typically used to
penetrate the case, while the remainder of the drill body removes
material from the casehardened material's softer core. Therefore,
the chisel edge of conventional drills of monolithic construction
used in that application will wear at a much faster rate than the
remainder of the cutting edge, resulting in a relatively short
service life for such drills. In both instances, because of the
monolithic construction of conventional cemented carbide drills,
frequent regrinding of the cutting edge is necessary, thus placing
a significant limitation on the service life of the bit. Frequent
regrinding and tool changes also result in excessive downtime for
the machine tool that is being used.
[0009] Therefore, composite articles, such as composite rotary
tools have been used, such as those tools described in described in
U.S. Pat. No. 6,511,265 which is hereby incorporated by reference
in its entirety. If designed properly, composite rotary tools may
have increased tool service life as compared to rotary tools having
a more monolithic construction. However, there exists a need for
drills and other rotary tools that have different characteristics
at different regions of the tool and comprise coolant channels. As
an example, a need exists for cemented carbide drills and other
rotary tools that will experience substantially even wear
regardless of the position on the tool face relative to the axis of
rotation of the tool and allow cooling at the cutting surfaces.
There is a need for a composite rotary tool having coolant channels
so composite rotary tools may have the same benefits as monolithic
rotary tools. There is also a need for a versatile method of
producing composite rotary tools and composite rotary tools
comprising coolant channels.
SUMMARY
[0010] Embodiments of the present invention include composite
articles comprising at least a first region and a second region.
The first region may comprise a first composite material, wherein
the first region comprises less than 5 wt. % cubic carbides by
weight, and the second region may comprise a second composite
material, wherein the second composite material differs from the
first composite material in at least one characteristic. The
composite article may additionally comprise at least one coolant
channel. In certain embodiments, the first and second composite
material may individually comprise hard particles in a binder,
wherein the hard particles independently comprise at least one of a
carbide, a nitride, a boride, a silicide, an oxide, and solid
solutions thereof and the binder comprises at least one metal
selected from cobalt, nickel, iron and alloys thereof. In specific
embodiments, the first composite material and the second composite
material may individually comprise metal carbides in a binder.
[0011] The characteristic may be at least one characteristic
selected from the group consisting of modulus of elasticity,
hardness, wear resistance, fracture toughness, tensile strength,
corrosion resistance, coefficient of thermal expansion, and
coefficient of thermal conductivity. The composite article may be
one of rotary tool, a rotary tool blank, a drill, an end mill, a
tap, a rod, and a bar, for example. In some embodiments, the
composite article may further comprises two or more coolant
channels and the coolant channels may be substantially straight or
substantially helical shape.
[0012] Embodiments of the present invention further include a
method of forming an article, comprising coextruding at least two
composite materials comprising metal carbides to form a green
compact. The composite materials may be as described above. The
coextruding at least two composite materials may be performed
through a die and, in certain embodiments, the die may comprise
means for making internal channels in the green compact. The die
may comprise at least one wire to form an internal channel within
the green compact, wherein the wire may be rigid or flexible.
[0013] Embodiments also include a method of producing a rotary tool
having a composite structure comprising placing an extruded first
powder metal into a first region of a void of a mold, placing a
second metallurgical powder metal into a second region of the void,
the extruded first powder metal differing from the second
metallurgical powder, and compressing the mold to consolidate the
extruded first powder metal and the second powder metal to form a
green compact. The green compact may be sintered to form the
article. Material may be removed material from the green compact to
provide at least one cutting edge prior to or after sintering.
[0014] The reader will appreciate the foregoing details and
advantages of the present invention, as well as others, upon
consideration of the following detailed description of embodiments
of the invention. The reader also may comprehend such additional
details and advantages of the present invention upon using the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The features and advantages of the present invention may be
better understood by reference to the accompanying drawings in
which:
[0016] FIGS. 1(a) and 1(b) are plan and on-end views, respectively,
of a conventional twist drill with coolant channels;
[0017] FIG. 2(a) is a graph indicating cutting speeds at the three
diameters D1, D2, and D3 of a conventional twist drill indicated in
FIG. 2(b);
[0018] FIGS. 3(a) and (b) include a transverse section (FIG. 3(a)
and a longitudinal section (FIG. 3(b)) of rods produced by
embodiments of the method of the present invention comprising a
core of centered carbide grade B and a shell of cemented carbide
grade A;
[0019] FIGS. 4(a)-(d) are representations of a cross-sectional
views of an embodiments of a composite cemented carbide;
[0020] FIGS. 5(a)-(d) are embodiments of blanks showing examples of
the different configurations of coolant channels, such as a
straight single coolant channel (FIG. 5(a)); two straight channels
(FIG. 5(b)); two helical or spiral channels (FIG. 5(c)); and three
helical or spiral channels (FIG. 5(d));
[0021] FIG. 6(a) is a representation of the coextrusion pressing
apparatus used in coextrusion of a tube of grade A and a rod of
grade B through a die with internal spiral serrations to produce a
blank with helical or spiral channels.
[0022] FIG. 6(b) is a representation of a channel die;
[0023] FIG. 6(c) is a photograph of a coextruded composite cemented
carbide rod with internal channels exiting from a die with spiral
serrations;
[0024] FIG. 7 is representation of a dry bag isostatic pressing
apparatus used in an embodiment of a method of the present
invention including consolidating cemented carbide grade B with an
extruded rod with internal channels made from a cemented carbide
grade A;
[0025] FIG. 8(a) is a photograph of a longitudinal cross-section of
a composite rod with internal coolant channels of the present
invention, the nylon wires in the photograph have been inserted in
the channels to more clearly show their location and the path of
the coolant channels; and
[0026] FIG. 8(b) is a photograph of a longitudinal cross-section of
a drill made from a composite cemented carbide having internal
coolant channels.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0027] The present invention provides rotary cutting tools, cutting
tool blanks, rods, and other articles having a composite
construction and a method of making such articles. The articles may
further comprise internal channels, such as coolant channels, if
desired. As used herein, a rotary tool is a tool having at least
one cutting edge that is driven to rotate. As used herein,
"composite" construction refers to an article having regions
differing in chemical composition and/or microstructure. These
differences result in the regions having properties differing with
respect to at least one characteristic. The characteristic may be
at least one of, for example, hardness, tensile strength, wear
resistance, fracture toughness, modulus of elasticity, corrosion
resistance, coefficient of thermal expansion, and coefficient of
thermal conductivity. Composite rotary tools that may be
constructed as provided in the present invention include drills and
end mills, as well as other tools that may be used in, for example,
drilling, reaming, countersinking, counterboring, end milling, and
tapping of materials.
[0028] The present invention more specifically provides a composite
rotary tool having at least one cutting edge, at least two regions
of cemented carbide material that differ with respect to at least
one characteristic, and at least one coolant channel. The differing
characteristics may be provided by variation of at least one of the
chemical composition and the microstructure among the two regions
of cemented carbide material. The chemical composition of a region
is a function of, for example, the chemical composition of the
ceramic component and/or binder of the region and the
carbide-to-binder ratio of the region. For example, one of the two
cemented carbide material regions of the rotary tool may exhibit
greater wear resistance, enhanced hardness, and/or a greater
modulus of elasticity than the other of the two regions.
[0029] Aspects of present invention may be described in relation to
the tool blank 400, shown in FIG. 4(a) in a cross-sectional view
transverse to the axis. The tool blank 400 is a generally
cylindrical sintered compact with two coaxially disposed cemented
carbide regions 410, 420 and coolant channels 430. It will be
apparent to one skilled in the art, however, that the following
discussion of the present invention also may be adapted to the
fabrication of composite rotary tools and tool blanks having more
complex geometry and/or more than two regions. Thus, the following
discussion is not intended to restrict the invention, but merely to
illustrate embodiments of it.
[0030] In the embodiment of FIG. 4(a), the cylindrical rotary tool
blank 400 is comprised of two differing cemented carbide regions, a
core region 400 and an outer region 410. The core region 420 and
the outer region 410 are both of a cemented carbide material
including ceramic particles in a continuous matrix of binder.
Preferably, the cemented carbide materials in the core region 420
and in the outer region 410 include a ceramic component composed of
carbides of one or more elements belonging to groups IVB through
VIB of the periodic table including less than 5% cubic carbides or,
in some applications, less than 3 wt. % cubic carbides. Embodiments
of the present invention may comprise less than 5 wt. % cubic
carbides because cubic carbides may reduce strength transverse
rupture strength of the article, increase the production costs, and
reduce the fracture toughness. This is especially important for
tools used to machine hard work pieces where the machining results
in a shearing action and the strength of the drill should be the
greatest.
[0031] The ceramic component preferably comprises about 60 to about
98 weight percent of the total weight of the cemented carbide
material in each region. The carbide particles are embedded within
a matrix of binder material that preferably constitutes about 2 to
about 40 weight percent of the total material in each region. The
binder preferably is one or more of Co, Ni, Fe, and alloys of these
elements. The binder also may contain, for example, elements such
as W, Cr, Ti, Ta, V, Mo, Nb, Zr, Hf, and C up to the solubility
limits of these elements in the binder. Additionally, the binder
may contain up to 5 weight percent of elements such as Cu, Mn, Ag,
Al, and Ru. One skilled in the art will recognize that any or all
of the constituents of the cemented carbide material may be
introduced in elemental form, as compounds, and/or as master
alloys.
[0032] The core region 420 of the tool blank 400 is autogenously
bonded to the outer region 410 at an interface 415. The interface
440 is shown in FIG. 4(a) to be cylindrical, but it will be
understood that the shapes of the interfaces of cemented carbide
material regions of the composite rotary tools of the present
invention are not limited to cylindrical configurations. The
autogenous bond between the regions at the interface 415 may be
formed by, for example, a matrix of binder that extends in three
dimensions from the core region 420 to the outer region 410, or
vice versa. The ratio of binder to ceramic component in the two
regions may be the same or different and may be varied between the
regions to affect the regions' relative characteristics. By way of
example only, the ratio of binder to ceramic component in the
adjacent regions of the composite tool blank 30 may differ by 1 to
10 weight percent. The characteristics of the cemented carbide
materials in the different regions of the composite rotary tools of
the present invention may be tailored to particular
applications.
[0033] One skilled in the art, after having considered the
description of present invention, will understand that the improved
rotary tool of this invention could be constructed with several
layers of different cemented carbide materials to produce a
progression of the magnitude of one or more characteristics from a
central region of the tool to its periphery. Thus, for example, a
twist drill may be provided with multiple, coaxially disposed
regions of cemented carbide material and wherein each such region
has successively greater hardness and/or wear resistance than the
adjacent, more centrally disposed region. Coolant channels may be
provided in any of the regions or intersecting two or more regions.
The method of the present invention provides great design
flexibility in the design of extruded articles. Alternately, rotary
tools of the present invention could be made with other composite
configurations wherein differences in a particular characteristic
occur at different regions of the tool.
[0034] A major advantage of the composite cemented carbide rotary
tools of the present invention is the flexibility available to the
tool designer to tailor properties of regions of the tools to suit
different applications. For example, the size, location, thickness,
geometry, and/or physical properties of the individual cemented
carbide material regions of a particular composite blank of the
present invention may be selected to suit the specific application
of the rotary tool fabricated from the blank. In addition, the
coolant channels may be located in the desired locations and be
helical, spiral, linear, or a combination of such shapes. Thus, for
example, the stiffness of one or more cemented carbide regions of
the rotary tool experiencing significant bending during use may be
of a cemented carbide material having an enhanced modulus of
elasticity; the hardness and/or wear resistance of one or more
cemented carbide regions having cutting surfaces and that
experience cutting speeds greater than other regions may be
increased; and/or the corrosion resistance of regions of cemented
carbide material subject to chemical contact during use may be
enhanced.
[0035] FIGS. 4(b) and 4(c) show additional embodiments of the
present invention. These embodiments may additional comprise
channels, such as coolant channels. The embodiment of FIG. 4(b)
comprises a tube with internal regions of different cemented
carbide grades. In this example, the rod 440 comprises an outer
region 441 of a first cemented carbide, a first inner region 442 of
a second cemented carbide, and an additional inner regions 443 that
could comprise the same or different cemented carbides. The rod 440
could be produced, for example, by coextuding a set 450 comprising
a tube 451 filled with rods 452 and 453. Rods 452 may be formed
from a cemented carbide that has at least one characteristic that
differs from the rods 453, for example.
[0036] By way of example only, additional embodiments of rotary
tools of the present invention are shown in FIGS. 4 and 5. FIG. 4
depicts a step drill 110 constructed according to the present
invention. The drill 110 includes a cutting portion 112 including
several helically oriented cutting edges 114. The drill 110 also
includes a mounting portion 116 that is received by a chuck to
mount the drill to a machine tool (not shown). The drill 110 is
shown in partial cross-section to reveal three regions of cemented
carbide materials that differ relative to one another with regard
to at least one characteristic. A first region 118 is disposed at
the cutting tip of the drill 110. The cemented carbide material
from which region 118 is composed exhibits an enhanced wear
resistance and hardness relative to a central region 120 forming
the core of the drill 110. The core region is of a cemented carbide
material that exhibits an enhanced modulus of elasticity relative
to the remaining two regions. The enhanced modulus of elasticity
reduces the tendency of the drill 110 to bend as it is forced into
contact with a work piece. The drill also includes an outer region
122 that defines the several helically oriented cutting edges 114.
The outer region surrounds and is coaxially disposed relative to
the core region 120. The outer region 122 is composed of a cemented
carbide material that exhibits enhanced hardness and wear
resistance relative to both the core region 120 and the tip region
118. The cutting surfaces 114 that are defined by the outer region
122 experience faster cutting speeds than cutting regions proximate
to the drill's central axis. Thus, the enhanced wear resistance and
hardness of the outer region 122 may be selected so that uniformity
of wear of the cutting surfaces is achieved.
[0037] Embodiments of the present invention also include additional
methods of making composite cemented carbide articles. Embodiments
include a method of forming a composite article by coextruding at
least two composite materials comprising cemented carbides to form
a green compact. The coextruding may be performed by direct or
indirect extrusion process. The feed chamber of the extruder is
filled with two grades of materials, such as two grades of carbide
powder and binder powder mixed with a plastic binder. The plastic
binder material may be present in concentrations from about 33 wt.
% to 67 wt. % and decreases the viscosity of the powder metal
mixture to allow extrusion.
[0038] The extrusion process for cemented carbides is well known in
the art. In a typical extrusion process, metal powders are mixed
with a plastic binder. Any typical plastic binder may be used such
as plastic binders based upon benzyl alcohol, cellulose, polymers,
or petroleum products. Typically, a high sheen mixing process is
used to ensure intimate contact between the metal powders and the
plastic binder.
[0039] The metal/binder mixer may then be pumped by screw feeder
through the extruder to produce an extruded product. Embodiments of
the method of the present invention include coextrusion of at least
two cemented carbide grades. The term coextrusion, as used herein,
means that two materials are extruded simultaneously to form a
single article incorporating both materials. Any coextrusion
process may be used in the method of the present invention such as,
pumping two grades of cemented carbide to separate sections of
funnel or die wherein the two grades exit the die in intimate
contact with each other.
[0040] An embodiment of the coextrusion process is shown in FIG.
6(a). The feed chamber 600 is filled with a rod 610 of a first
grade of cemented carbide powder and a tube 620 of a second grade
of cemented carbide powder. The rod 610 and the tube 620 were
individually formed by separate extrusion processes as known in
art. In certain embodiments, the tube 620 may be extruded directly
into the feed chamber 600. The rod 610, formed in a separate
extrusion process may then be inserted into the tube 620 already in
the feed chamber 600.
[0041] In this embodiment of the extrusion process, a plunger (not
shown) pushes the rod 610 and the tube 620 through the feed chamber
and into the funnel 630. The funnel 630 reduces in cross-sectional
area from the feed chamber to the die 640. The funnel 630 causes
compaction and consolidation of the cemented carbide powders
resulting in intimate contact between the rod 610 and tube 620 and
formation of a green compact ("extruded material").
[0042] In certain embodiments, the extrusion process may also
include a channel die 650 incorporated between the funnel 630 and
the die 640. The channel die comprises two wires 660 or the channel
die may comprise other means for making internal channels in the
green compact. The wires 660 are connected to arms 670 which hold
the wires 660 so they may contact the extruded material. The wires
660 result in the formation of channels in the extruded material.
The wires 660 may be made from any material capable of forming
channels in the extruded material, such as, but not limited to,
nylon, polymer coated metal wire, polyethylene, high density
polyethylene, polyester, polyvinyl chloride, polypropylene, an
aramid, Kevlar, polyetheretherketone, natural materials, cotton,
hemp, and jute. Preferably in certain applications, such as for
formation of helically oriented channels, the wire is a flexible
wire. However, for linearly oriented channels and in some helical
applications, rigid wires may be used. The channels may be used as
coolant channels in rotary tools. The wires 660 may be used to form
helically oriented channels, linearly oriented channels, or a
combination thereof. A cross-section of the wire or other channel
making component may be any shape, such as round, elliptical,
triangular, square, and hexagonal.
[0043] Helically oriented channels may be formed in the extruded
material in embodiments where the extruded material rotates
relative to the channel die 650. The extruded material may be
rotated by incorporating spiral serrations in the die 640. In FIG.
6(c), extruded material 680 exits die 645 that includes helical
serrations on the internal surface of the die 645. As the extruded
material passes over the serrations, the extruded material is
caused to rotate relative to the channel die (not shown).
Alternatively, the die may rotate to cause the extruded material to
rotate relative to the channel die. Other channel dies may be used,
such dies comprising fixed helical coils wherein the extruded
material is cause to rotate relative to the channel die in the same
rotation as the helical coils, or any other channel forming
means.
[0044] The channel die may be a separate component or may be
integral to the funnel, die, or other component in the extrusion
system. The channel die may be capable of making at least one
channel in the extruded material. The number and size of the
channels may be limited by the size of the extruded material, the
size of the channels, and the application for the ultimate use of
the extruded material. In embodiments comprising a channel die
comprising wires, the number of wires will correspond to the number
of channels formed in the extruded material. For an rotary tool
application, it may be preferable to have an equal number of
channels as there will be flutes for example.
[0045] Embodiments of the present invention may further include
loading the feed chamber with at least two cemented carbide grades.
At least one cemented carbide grade loaded in the feed chamber may
be an extruded form of either a rod, tube, bar, strips, rectangles,
gear profiles, star shapes, or any other shape that may be formed
in an extrusion process. In rotary tool or roller applications, it
may be preferable that at least one of the two cemented carbide
grades be in the form of a rod shape and at least one cemented
carbide in a shape of a tube. In other applications, the feed
chamber may be filled with multiple tubes and/or multiple rods of
different cemented carbide grades. If multiple rods are used, the
extruded material may be formed with specific grades of cemented
carbides in specific regions or randomly distributed throughout the
cross-section of the extruded material.
[0046] A further embodiment of the present invention may comprise
extruding a cemented carbide grade to form an extruded green
compact and pressing the extruded green compact with a second
cemented carbide grade to form a pressed green compact. The
extruded green compact may optionally comprise internal channels
formed as described above, for example.
[0047] Actual examples of application of the foregoing method to
provide composite rotary tools according to the present invention
follow.
[0048] Although the present invention has been described in
connection with certain embodiments, those of ordinary skill in the
art will, upon considering the foregoing description, recognize
that many modifications and variations of the invention may be
employed. All such variations and modifications of the present
invention are intended to be covered by the foregoing description
and the following claims.
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