U.S. patent application number 11/504847 was filed with the patent office on 2007-08-16 for methods for preparing metallurgical powder compositions and compacted articles made from the same.
This patent application is currently assigned to Hoeganaes Corporation. Invention is credited to Francis G. Hanejko.
Application Number | 20070186722 11/504847 |
Document ID | / |
Family ID | 38288128 |
Filed Date | 2007-08-16 |
United States Patent
Application |
20070186722 |
Kind Code |
A1 |
Hanejko; Francis G. |
August 16, 2007 |
Methods for preparing metallurgical powder compositions and
compacted articles made from the same
Abstract
Provided are methods of preparing high density compacted
components that increase that lubricity of metallurgical powder
compositions while reducing the overall organic content of the
compacted component. Method of preparing high density compacted
components having a high density include the steps of providing a
metallurgical powder composition having particles at least
partially coated with a metal phosphate layer, and compacting the
metallurgical powder composition in the die at a pressure of at
least about 5 tsi. The metallurgical powder composition comprises a
base-metal powder, optional alloying powders, and a particulate
internal lubricant. The metal phosphate at least partially coats
the base-metal powder, the optional alloying powder, or both. The
metal phosphate coating increases the lubricity of metallurgical
powders without the need for large quantities of organic material,
e.g., lubricants and binders.
Inventors: |
Hanejko; Francis G.;
(Marlton, NJ) |
Correspondence
Address: |
WOODCOCK WASHBURN LLP
CIRA CENTRE, 12TH FLOOR
2929 ARCH STREET
PHILADELPHIA
PA
19104-2891
US
|
Assignee: |
Hoeganaes Corporation
Cinnaminson
NJ
|
Family ID: |
38288128 |
Appl. No.: |
11/504847 |
Filed: |
August 15, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60758354 |
Jan 12, 2006 |
|
|
|
Current U.S.
Class: |
75/252 |
Current CPC
Class: |
B22F 3/12 20130101; B22F
2001/0066 20130101; C22C 33/0207 20130101; Y10T 428/2991 20150115;
B22F 2998/10 20130101; B22F 3/02 20130101; Y10T 428/2993 20150115;
B22F 1/0059 20130101; Y10T 428/2998 20150115; B22F 2998/10
20130101; B22F 1/02 20130101; B22F 2999/00 20130101; B22F 2999/00
20130101; B22F 1/0059 20130101; B22F 1/02 20130101; B22F 3/10
20130101; B22F 1/02 20130101; B22F 3/02 20130101; B22F 1/0088
20130101 |
Class at
Publication: |
075/252 |
International
Class: |
C22C 1/05 20060101
C22C001/05 |
Claims
1. A metallurgical powder composition comprising: (a) at least 85
weight percent of a base-metal powder; (b) from about 0.01 to about
1.0 weight percent, based on the weight of the base-metal powder,
of metal phosphate that at least partially coats the base-metal
powder.
2. The metallurgical powder composition of claim 1, further
comprising a particulate internal lubricant.
3. The metallurgical powder composition of claim 2, wherein the
particulate internal lubricant is a polyamide, a C.sub.5 to
C.sub.30 fatty acid, a metal salt of a polyamide, a metal salt of a
C.sub.5 to C.sub.30 fatty acid, an ammonium salt of a C.sub.5 to
C.sub.30 fatty acid, lithium stearate, zinc stearate, manganese
stearate, calcium stearate, ethylene bis-stearamide, polyethylene
wax, polyolefin, or combinations thereof.
4. The metallurgical powder composition of claim 2, wherein the
particulate internal lubricant comprises: (i) a polyamide
lubricant, and (ii) a stearate lubricant.
5. The metallurgical powder composition of claim 2, wherein the
particulate internal lubricant comprises: about 0.2 weight percent
of a polyamide lubricant composed of ethylene bis-stearamide having
an initial melting point between about 200.degree. C. and
300.degree. C., and about 0.2 weight percent of Kenolube.TM..
6. The metallurgical powder composition of claim 1, further
comprising: about 0.10 weight percent binding agent, wherein the
particulate internal lubricant comprises: about 0.15 weight percent
of a polyamide lubricant composed of ethylene bis-stearamide having
an initial melting point between about 200.degree. C. and
300.degree. C., and about 0.15 weight percent of Kenolube.TM..
7. The metallurgical powder composition of claim 2, wherein the
particulate internal lubricant is present in an amount from about
0.01 to about 2.0 weight percent by weight of base-metal
powder.
8. The metallurgical powder composition of claim 1, wherein said
metal phosphate is manganese zinc phosphate, nickel phosphate, zinc
phosphate, copper phosphate, or combinations thereof.
9. The metallurgical powder composition of claim 1, wherein the
metal phosphate is present in an amount from about 0.05 to about
0.40 weight percent by weight of base-metal powder.
10. The metallurgical powder composition of claim 1, wherein the
base-metal powder is an iron based powder.
11. The metallurgical powder composition of claim 10, wherein the
iron based powder comprises an alloying powder.
12. The metallurgical powder composition of claim 10, wherein the
iron based powder is a prealloyed iron base powder.
13. The metallurgical powder composition of claim 10, wherein the
iron based powder is a diffusion bonded iron based powder.
14. The metallurgical powder composition of claim 1, wherein the
iron based powder is a ferromagnetic powder.
15. A compacted article comprising a compacted metallurgical powder
composition comprising: (i) at least 85 weight percent of a
base-metal powder; (ii) from about 0.01 to about 1.0 weight
percent, based on the weight of the base-metal powder, of metal
phosphate that at least partially coats the base-metal powder.
16. The compacted article of claim 15, wherein the compacted
article is sintered.
17. The compacted article of claim 15, wherein the metal phosphate
is manganese zinc phosphate, nickel phosphate, copper phosphate, or
zinc phosphate.
18. A method of preparing a metallurgical powder composition
comprising: (a) providing a base-metal powder, (b) providing a
coating solution of metal phosphate and protonic acid, and (c)
contacting the iron based particles with the coating solution so as
to at least partially coat said iron particles with the metal
phosphate.
19. The method of preparing a metallurgical powder composition of
claim 18, further comprising a step of providing a particulate
internal lubricant.
20. The method of preparing a metallurgical powder composition of
claim 19, wherein the metallurgical powder composition comprises
from about 0.01 to about 2.0 weight percent by weight of a
particulate internal lubricant.
21. The method of preparing a metallurgical powder composition of
claim 18 further comprising the step of admixing a particulate
internal lubricant with the base metal powder prior to being coated
with the metal phosphate, the particulate internal lubricant
thereby also being contacted with the coating solution.
22. The method of preparing a metallurgical powder composition of
claim 18 further comprising the step of admixing a particulate
internal lubricant with the base metal powder after the base metal
powder is coated with the metal phosphate.
23. The method of preparing a metallurgical powder composition of
claim 19 wherein the base-metal powder is bonded with about 0.10
weight percent binding agent, and the particulate internal
lubricant comprises: about 0.15 weight percent of a polyamide
lubricant composed of ethylene bis-stearamide having an initial
melting point between about 200.degree. C. and 300.degree. C., and
about 0.15 weight percent of Kenolube.TM..
24. The method of preparing a metallurgical powder composition of
claim 19, wherein the particulate internal lubricant comprises:
about 0.2 weight percent of a polyamide lubricant composed of
ethylene bis-stearamide having an initial melting point between
about 200.degree. C. and 300.degree. C., and about 0.2 weight
percent of Kenolube.TM..
25. The method of preparing a metallurgical powder composition of
claim 18, further comprising a step of admixing an alloying powder
with the base metal powder after the base metal powder is coated
with the metal phosphate.
26. The method of preparing a metallurgical powder composition of
claim 25, wherein the alloying powder comprises graphite, Ni, Cu,
FeP, ferroalloy, or combinations thereof.
27. The method of preparing a metallurgical powder composition of
claim 18, wherein the metallurgical powder composition comprises
from about 0.05 to about 1.0 weight percent of metal phosphate.
28. The method of preparing a metallurgical powder composition of
claim 18, wherein the base-metal powder is an iron based
powder.
29. The method of preparing a metallurgical powder composition of
claim 28, wherein the iron based powder comprises an alloying
powder.
30. The method of preparing a metallurgical powder composition of
claim 28, wherein the iron based powder is a prealloyed iron base
powder.
31. The method of preparing a metallurgical powder composition of
claim 28, wherein the iron based powder is a diffusion bonded iron
based powder.
32. The method of preparing a metallurgical powder composition of
claim 28, wherein the iron based powder is a ferromagnetic
powder.
33. Methods of preparing compacted articles comprising the steps
of: (a) providing a metallurgical powder composition comprising:
(i) at least 85 weight percent of a base-metal powder; and (ii)
from about 0.01 to about 1.0 weight percent, based on the weight of
the base-metal powder, of metal phosphate that at least partially
coats the base-metal powder; (b) compacting the metallurgical
powder composition in a die at a pressure of at least about 5
tsi.
34. The methods of preparing compacted articles of claim 33,
further comprising the step of sintering the compact part.
35. The methods of preparing compacted articles of claim 33,
wherein said metal phosphate is manganese zinc phosphate, nickel
phosphate, zinc phosphate, copper phosphate, or combinations
thereof.
36. The methods of preparing compacted articles of claim 33,
wherein the metal phosphate is present in an amount from about 0.05
to about 0.40 weight percent by weight of base-metal powder.
37. The methods of preparing compacted articles of claim 33,
wherein the metallurgical powder composition further comprises a
particulate internal lubricant.
38. The methods of preparing compacted articles of claim 37,
wherein the particulate internal lubricant is present in an amount
from about 0.01 to about 2.0 weight percent by weight of base-metal
powder.
39. The methods of preparing compacted articles of claim 37,
wherein the particulate internal lubricant is a polyamide, a
C.sub.5 to C.sub.30 fatty acid, a metal salt of a polyamide, a
metal salt of a C.sub.5 to C.sub.30 fatty acid, an ammonium salt of
a C.sub.5 to C.sub.30 fatty acid, lithium stearate, zinc stearate,
manganese stearate, calcium stearate, ethylene bis-stearamide,
polyethylene wax, polyolefin or combinations thereof.
40. The methods of preparing compacted articles of claim 33,
wherein the base-metal powder is an iron based powder.
41. The methods of preparing compacted articles of claim 33,
wherein the iron based powder comprises an alloying powder.
42. The methods of preparing compacted articles of claim 40,
wherein the iron based powder is a prealloyed iron base powder.
43. The methods of preparing compacted articles of claim 40,
wherein the iron based powder is a diffusion bonded iron based
powder.
44. The methods of preparing compacted articles of claim 40,
wherein the iron based powder is a ferromagnetic powder.
45. The methods of preparing compacted articles of claim 33,
wherein the base-metal powder is coated by the steps comprising:
(a) providing a base-metal powder, (b) providing a coating solution
of metal phosphate and protonic acid, (c) contacting the iron based
particles with the coating solution to at least partially coat said
iron particles with the metal phosphate.
46. The methods of preparing compacted articles of claim 45,
wherein the protonic acid is diluted in acetone.
47. The methods of preparing compacted articles of claim 45,
wherein the protonic acid is sulphuric acid, nitric acid,
hydrochloric acid, phosphoric acid, or combinations thereof.
48. The methods of preparing compacted articles of claim 33,
further comprising the step of sintering the compacted
metallurgical powder composition.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Application Ser.
No. 60/758,354, filed Jan. 12, 2006, the entire disclosure of which
is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to methods of making compacted
powder metallurgical components and powder metallurgical components
made from such methods. More particularly, the present invention is
directed to methods of reducing the organic content of high density
compacted powder metallurgical components and powder metallurgical
components made from such methods.
BACKGROUND OF THE INVENTION
[0003] Iron-based particles have long been used as a base material
in the manufacture of structural components by powder metallurgical
methods. The iron-based particles are first molded in a die under
high pressures in order to produce a desired shape. After the
molding step, the structural component may undergo a sintering step
to impart additional strength.
[0004] Research in the powder metallurgical manufacture of
compacted components using iron-based powders has been directed to
the development of iron powder compositions that enhance certain
physical and magnetic properties without detrimentally affecting
other properties. Desired properties that often must be balanced
include, for example, high density and strength, and ease of
removing a part from a compacting die. Desirable properties for
magnetic parts include, for example, a high permeability through an
extended frequency range, high pressed strength, low core losses,
and suitability for compression molding techniques.
[0005] Compaction of powder metallurgical compositions is carried
out within a die cavity that is subjected to extreme pressures. To
avoid excessive wear on the die cavity, lubricants are commonly
used during the compaction process. However, most known lubricants
detrimentally affect the physical properties of compact parts. For
example, use of lubricants often reduces the green strength of
green compacts. It is believed that during compaction an internal
lubricant is exuded between iron and/or alloying metal particles
such that it fills the pore volume between the particles and
interferes with particle-to-particle bonding. Indeed, some shapes
cannot be pressed using known internal lubricants. Tall,
thin-walled bushings, for example, require large amounts of
internal lubricant to overcome die wall friction and reduce the
required ejection force. Such levels of internal lubricant,
however, typically reduce green strength to the point that the
resulting compacts crumble upon ejection. Also, internal lubricants
often adversely affect powder flow rate and apparent density, as
well as green density of the compact, particularly at higher
compaction pressures. Moreover, excessive amounts of internal
lubricants can lead to compacts having poor dimensional integrity,
and volatized lubricant can form soot on heating surfaces of the
sintering furnace.
[0006] To avoid problems associated with internal lubricants, it is
known to use an external spray lubricant rather than an internal
lubricant. However, use of external lubricants increases compaction
cycle time and leads to less uniform compaction. It is readily
known to those skilled in the art that the inherent variability of
using an external lubricant limits the commercial usefulness of
such fabrication techniques. These limitations are especially
prevalent in techniques for fabricating high density parts.
[0007] Accordingly, there exists a need in the art for methods of
preparing high density compacted components that are easily ejected
from die cavities.
SUMMARY OF THE INVENTION
[0008] Provided are methods of preparing high density compacted
components that increase the lubricity of metallurgical powder
compositions while reducing the overall organic content of the
compacted component. Methods of preparing high density compacted
components include the steps of providing a metallurgical powder
composition having base metal particles at least partially coated
with a metal phosphate layer, and compacting the metallurgical
powder composition in a die at a pressure of at least about 5
tsi.
[0009] The metallurgical powder composition comprises a base-metal
powder, optional alloying powders, and a particulate internal
lubricant. The metal phosphate at least partially coats the
base-metal powder, the optional alloying powder, or both. The metal
phosphate coating increases the lubricity of metallurgical powders
without the need for large quantities of organic material, e.g.,
lubricants and binders. Without being limited by theory, it is
believed that the metal phosphate coating traps lubricant particles
on the surface of metal particles and compacted parts and thereby
increases lubricity. The present methods are especially useful in
drawing operations and when compaction temperatures exceed room
temperature.
[0010] Metal phosphates include for example, manganese phosphate,
zinc phosphate, nickel phosphate, copper phosphate, and
combinations thereof. Particulate internal lubricants include, for
example, polyamides, C.sub.5 to C.sub.30 fatty acids, metal salts
of polyamides, metal salts of C.sub.5 to C.sub.30 fatty acids,
ammonium salts of C.sub.5 to C.sub.30 fatty acids, lithium
stearate, zinc stearate, manganese stearate, calcium stearate,
ethylene bis-stearamide, polyethylene waxes, polyolefins, and
combinations thereof.
[0011] In one embodiment, metallurgical powder compositions include
less than about 0.5 weight percent of a particulate internal
lubricant and provide sintered compacted components having a
density of at least about 7.4 g/cm.sup.3.
[0012] In another embodiment, metallurgical powder compositions are
composed of a base metal powder bonded with a particulate internal
lubricant containing an amide lubricant. The metallurgical powder
composition is composed of 0.40 weight percent total organic
materials, such as for example, 0.10 weight percent binding agent,
about 0.15 weight percent of a polyamide lubricant composed of
ethylene bis-stearamides having an initial melting point between
about 200.degree. C. and 300.degree. C., and about 0.15 weight
percent of polyamide lubricant composed of an admixture of ethylene
bisstearamide and zinc stearate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a graph of ejection pressure verses time for
compacts prepared from an exemplary metallurgical powder
composition when compressed at four different compaction
pressures.
[0014] FIG. 2 is a graph of ejection pressure verses time comparing
compacts prepared from an exemplary metallurgical powder
composition and compacts prepared from a conventional metallurgical
powder composition.
[0015] FIG. 3 is another graph of ejection pressure verses time
comparing compacts prepared from an exemplary metallurgical powder
composition and compacts prepared from a conventional metallurgical
powder composition.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0016] Described are methods of preparing high density compacted
components and compacted components made therefrom. Methods of
preparing high density compacted components include the steps of
providing a metallurgical powder composition having particles at
least partially coated with a metal phosphate layer, and compacting
the metallurgical powder composition in a die. The metallurgical
powder composition comprises a base-metal powder, optional alloying
powders, and a particulate internal lubricant. The metal phosphate
at least partially coats the base-metal powder, the optional
alloying powder, or both. The described methods provide high
density compacted components that increase the lubricity of
metallurgical powder compositions while reducing the overall
organic lubricant content of compacted parts.
[0017] Base-metal powders are any base-metal powder, or a blend of
more than one powder, of the kind generally used in the powder
metallurgy industry. Base-metal powders include, for example,
iron-based powders and nickel based powders. Preferably, the
base-metal powder is an iron-based powder.
[0018] Examples of "iron-based" powders, as that term is used
herein, are powders of substantially pure iron, powders of iron
pre-alloyed with other elements (for example, steel-producing
elements) that enhance the strength, hardenability, electromagnetic
properties, or other desirable properties of the final product, and
powders of iron to which such other elements have been diffusion
bonded. The iron based powder can be a mix of an atomized iron
powder and a sponge iron, or other type of iron powder.
[0019] Substantially pure iron powders are powders of iron
containing not more than about 1.0% by weight, preferably no more
than about 0.5% by weight, of normal impurities. These
substantially pure iron powders are preferably atomized powders
prepared by atomization techniques. Examples of such highly
compressible, metallurgical-grade iron powders are the ANCORSTEEL
1000 series of pure iron powders, e.g. 1000, 1000B, and 1000C,
available from Hoeganaes Corporation, Riverton, N.J. For example,
ANCORSTEEL 1000 iron powder, has a typical screen profile of about
22% by weight of the particles below a No. 325 sieve (U.S. series)
and about 10% by weight of the particles larger than a No. 100
sieve with the remainder between these two sizes (trace amounts
larger than No. 60 sieve). The ANCORSTEEL 1000 powder has an
apparent density of from about 2.85-3.00 g/cm.sup.3, typically 2.94
g/cm.sup.3. Other substantially pure iron powders that can be used
in the invention are typical sponge iron powders, such as
Hoeganaes' ANCOR MH-100 powder.
[0020] The iron-based powder can incorporate one or more alloying
elements that enhance the mechanical or other properties of the
final metal part. Such iron-based powders can be powders of iron,
preferably substantially pure iron, that has been blended or
pre-alloyed with one or more such elements. Iron based powders also
include combinations of blended and prealloyed powders. Pre-alloyed
iron based powders are prepared by making a melt of iron and the
desired alloying elements, and then atomizing the melt, whereby the
atomized droplets form the powder upon solidification.
[0021] Examples of alloying elements that can be blended or
pre-alloyed with iron based powders include, but are not limited
to, molybdenum, manganese, magnesium, chromium, silicon, copper,
nickel, gold, vanadium, columbium (niobium), graphite, phosphorus,
aluminum, and combinations thereof. Preferred alloying elements are
molybdenum, phosphorus, nickel, silicon, and combinations thereof.
The amount of the alloying element or elements incorporated depends
upon the properties desired in the final metal part. Pre-alloyed
iron powders that incorporate such alloying elements are available
from Hoeganaes Corp. as part of its ANCORSTEEL line of powders,
e.g., ANCORSTEEL 50HP, 85HP, and 150HP, ANCORSTEEL 737, ANCORSTEEL
2000, ANCORSTEEL 4300, and ANCORSTEEL 4600V, FD4600, and
FD4600A.
[0022] Alloying powders that can be admixed with base-metal powders
are those known in the metallurgical powder field to enhance the
strength, hardenability, electromagnetic properties, or other
desirable properties of the final sintered product. Steel-producing
elements are among the best known of these materials. Exemplary
alloying materials are binary alloys of copper with tin or
phosphorus; ferro-alloys of iron with manganese, chromium, boron,
phosphorus, or silicon; low-melting ternary and quaternary
eutectics of carbon and two or three of iron, vanadium, manganese,
chromium, and molybdenum; carbides of tungsten or silicon; silicon
nitride; and sulfides of manganese or molybdenum. These alloying
powders are in the form of particles that are generally of finer
size than the particles of metal powder with which they are
admixed.
[0023] The alloying powders generally have a particle size
distribution such that they have a d.sub.90 value of below about
100 microns, preferably below about 75 microns, and more preferably
below about 50 microns; and a d.sub.50 value of below about 75
microns, preferably below about 50 microns, and more preferably
below about 30 microns. The amount of alloying powder present in
the composition will depend on the properties desired of the final
sintered part. Generally the amount will be minor, up to about 5%
by weight of the total powder composition weight, although as much
as 10-15% by weight can be present for certain specialized powders.
A preferred range suitable for most applications is about 0.25-4.0%
by weight. Particularly preferred alloying elements for use in the
present invention for certain applications are copper and nickel,
which can be used individually at levels of about 0.25-4% by
weight, and can also be used in combination.
[0024] An exemplary iron-based powder is a substantially pure iron
pre-alloyed with molybdenum (Mo). The powder is produced by
atomizing a melt of substantially pure iron containing from about
0.5 to about 2.5 weight percent Mo. An example of such a powder is
Hoeganaes' ANCORSTEEL 85HP steel powder, which contains about 0.85
weight percent Mo, less than about 0.4 weight percent, in total, of
such other materials as manganese, chromium, silicon, copper,
nickel, molybdenum or aluminum, and less than about 0.02 weight
percent carbon. Another example of such a powder is Hoeganaes'
ANCORSTEEL 4600V steel powder, which contains about 0.5-0.6 or
0.4-0.6 weight percent molybdenum, about 1.5-2.0 weight percent
nickel, and about 0.1 -0.25 weight percent manganese, and less than
about 0.02 weight percent carbon.
[0025] Another exemplary pre-alloyed iron-based powder is disclosed
in U.S. Pat. No. 5,108,493, which is herein incorporated by
reference in its entirety. This steel powder composition is an
admixture of two different pre-alloyed iron-based powders, one
being a pre-alloy of iron with 0.5-2.5 weight percent molybdenum,
the other being a pre-alloy of iron with carbon and with at least
about 25 weight percent of a transition element component, wherein
this component comprises at least one element selected from the
group consisting of chromium, manganese, vanadium, and columbium.
The admixture is in proportions that provide at least about 0.05
weight percent of the transition element component to the steel
powder composition. An example of such a powder is commercially
available as Hoeganaes' ANCORSTEEL 41 AB steel powder, which
contains about 0.85 weight percent molybdenum, about 1 weight
percent nickel, about 0.9 weight percent manganese, about 0.75
weight percent chromium, and about 0.5 weight percent carbon.
[0026] A further example of iron-based powders are diffusion-bonded
iron-based powders which are particles of substantially pure iron
that have a layer or coating of one or more other alloying elements
or metals, such as steel-producing elements, diffused into their
outer surfaces. A typical process for making such powders is to
atomize a melt of iron and then combine this atomized powder with
the alloying powders and anneal this powder mixture in a furnace.
Such commercially available powders include DISTALOY 4600A
diffusion bonded powder from Hoeganaes Corporation, which contains
about 1.8% nickel, about 0.55% molybdenum, and about 1.6% copper,
and DISTALOY 4800A diffusion bonded powder from Hoeganaes
Corporation, which contains about 4.05% nickel, about 0.55%
molybdenum, and about 1.6% copper.
[0027] Whether in a particulate, pre-alloyed, or diffusion-bonded
iron-based powder, the alloying elements are present in an amount
that depends on the properties desired of the final sintered part.
Generally, the amount of the alloying elements will be relatively
minor, up to about 5% by weight of the total powder composition
weight, although as much as 10-15% by weight can be used in certain
applications. A preferred range is typically between 0.25 and 4% by
weight.
[0028] Other iron-based powders that are useful in the practice of
the invention are ferromagnetic powders. An example is a powder of
iron pre-alloyed with small amounts of phosphorus.
[0029] The iron-based powders that are useful in the practice of
the invention also include stainless steel powders. These stainless
steel powders are commercially available in various grades in the
Hoeganaes ANCOR.RTM. series, such as the ANCOR.RTM. 303L, 304L,
316L, 410L, 430L, 434L, and 409Cb powders. Also, iron-based powders
include tool steels made by the powder metallurgy method.
[0030] Particles of iron-based powders, such as for example
substantially pure iron powders, diffusion bonded iron powders, and
pre-alloyed iron powders, have a distribution of particle sizes.
Typically, these powders are such that at least about 90% by weight
of the powder sample can pass through a No. 45 sieve (U.S. series),
and more preferably at least about 90% by weight of the powder
sample can pass through a No. 60 sieve. These powders typically
have at least about 50% by weight of the powder passing through a
No. 70 sieve and retained above or larger than a No. 400 sieve,
more preferably at least about 50% by weight of the powder passing
through a No. 70 sieve and retained above or larger than a No. 325
sieve. Also, these powders typically have at least about 5 weight
percent, more commonly at least about 10 weight percent, and
generally at least about 15 weight percent of the particles passing
through a No. 325 sieve.
[0031] As such, these powders can have a weight average particle
size as small as one micron or below, or up to about 850-1,000
microns, but generally the particles will have a weight average
particle size in the range of about 10-500 microns. Preferred are
iron or pre-alloyed iron particles having a maximum weight average
particle size up to about 350 microns; more preferably the
particles will have a weight average particle size in the range of
about 25-150 microns, and most preferably 80-150 microns. Reference
is made to MPIF Standard 05 for sieve analysis.
[0032] Base-metal powders can also include nickel-based powders.
Examples of "nickel-based" powders, as that term is used herein,
are powders of substantially pure nickel, and powders of nickel
pre-alloyed with other elements that enhance the strength,
hardenability, electromagnetic properties, or other desirable
properties of the final product. The nickel-based powders can be
admixed with any of the alloying powders mentioned previously with
respect to the iron-based powders. Examples of nickel-based powders
include those commercially available as the Hoeganaes
ANCORSPRAY.RTM. powders such as the N-70/30 Cu, N-80/20, and N-20
powders. These powders have particle size distributions similar to
the iron-based powders. Preerred nickel-based powders are those
made by an atomization process.
[0033] The described iron-based powders that constitute the
base-metal powder, or at least a major amount thereof, are, as
noted above, preferably atomized powders. These iron-based powders
have apparent densities of at least 2.75, preferably between 2.75
and 4.6, more preferably between 2.8 and 4.0, and in some cases
more preferably between 2.8 and 3.5 g/cm.sup.3.
[0034] Base metal powders constitute a major portion of the
metallurgical powder composition, and generally constitute at least
about 85 weight percent, preferably at least about 90 weight
percent, and more preferably at least about 95 weight percent of
the metallurgical powder composition.
[0035] A metal phosphate coating substantially, completely, or at
least partially covers the base metal powders, optional alloying
powders, or both. Metal phosphates include any metal phosphate
known to those skilled in the art. Metal phosphates include, for
example, manganese phosphate, nickel phosphate, zinc phosphate,
copper phosphate, and combinations thereof. Preferably, the metal
phosphate is zinc phosphate.
[0036] The metal phosphate coating increases the lubricity of
metallurgical powders without the need for high lubricant content,
i.e., organic content. Without being limited by theory it is
believed that the metal phosphate coating traps lubricant particles
on the surface of metal particles and compacted parts. The present
methods are especially useful in drawing operations and when
compaction temperature exceed room temperature.
[0037] Thus, metallurgical powder composition may be prepared that
exhibit higher pore free density and lower total organic content
compared to compositions that do not include a metal phosphate
coating. Lowering the total organic content of metallurgical powder
compositions is beneficial in that less organic material must be
removed during sintering. Further, metallurgical powder
compositions containing a metal phosphate coating exhibited higher
compressibility and green strength at compression temperatures
greater than 120.degree. F. For example, metallurgical powder
compositions exhibited green strength more than 100% compared to
compositions that did not include a metal phosphate coating.
[0038] Metallurgical powder compositions include from about 0.01 to
about 1 weight percent of metal phosphate. Preferably,
metallurgical powder compositions include from about 0.05 to about
0.40 weight percent of the metal phosphate. More preferably,
metallurgical powder compositions include from about 0.05 to about
0.20 weight percent of the metal phosphate.
[0039] Metallurgical powder compositions include particulate
internal lubricants. Particulate internal lubricants include
internal lubricants that are commonly known to those skilled in the
art. Particulate internal lubricants reduce the ejection forces
required to remove the compacted component form the compaction die
cavity. Examples of particulate internal lubricants include
stearate compounds, such as lithium, zinc, manganese, and calcium
stearates, waxes such as ethylene bis-stearamides, polyethylene
wax, polyolefins, amide lubricants, and mixtures of these types of
lubricants. Other lubricants include those containing a polyether
compound such as is described in U.S. Pat. No. 5,498,276 to Luk,
and those useful at higher compaction temperatures described in
U.S. Pat. No. 5,368,630 to Luk & U.S. Pat. No. 5,154,881 to
Rutz, in addition to those disclosed in U.S. Pat. No. 5,330,792 to
Johnson et al., each of which is incorporated herein in its
entirety by reference.
[0040] Although lithium stearate is utilized as a lubricant, some
embodiments require limited quantities, or exclusion of lithium
stearate. Without being limited by theory it is believed that
lithium stearate reacts with phosphoric acid to form a stearic acid
having a lower melting temperature compared to the lithium
stearate. This reaction may result in lower lubricity.
[0041] Amide lubricants, such as those disclose in U.S. Pat. No.
5,368,630 to Luk, are, in essence, high melting-point waxes.
Preferably, the amide lubricants are the condensation product of a
dicarboxylic acid, a monocarboxylic acid, and a diamine.
[0042] Dicarboxylic acids are linear acids having the general
formula HOOC(R)COOH where R is a saturated or unsaturated linear
aliphatic chain of 4-10, preferably about 6-8, carbon atoms.
Preferably, the dicarboxylic acid is a C.sub.8-C.sub.10 saturated
acid. More preferably, the dicarboxylic acid is sebacic acid. The
dicarboxylic acid is present in an amount of from about 10 to about
30 weight percent of the starting reactant materials.
[0043] Monocarboxylic acids are saturated or unsaturated
C.sub.10-C.sub.22 fatty acids. Preferably, the monocarboxylic acid
is a C.sub.12-C.sub.20 saturated acid. More preferably, the
monocarboxylic acid is stearic acid. A preferred unsaturated
monocarboxylic acid is oleic acid. The monocarboxylic acid is
present in an amount of from about 10 to about 30 weight percent of
the starting reactant materials.
[0044] Diamines are alkylene diamines, preferably of the general
formula (CH.sub.2).sub.x(NH.sub.2).sub.2 where x is an integer of
about 2-6. More preferably the diamine is ethylene diamine.
Diamines are present in an amount of from about 40 to about 80
weight percent of the starting reactant materials to form the amide
product.
[0045] The condensation reaction is preferably conducted at a
temperature of from about 260.degree. C. to about 280.degree. C.
and at a pressure up to about 7 atmospheres. The reaction is
preferably conducted in a liquid state. Under reaction conditions
at which diamines are in a liquid state, the reaction can be
performed in an excess of the diamine acting as a reactive solvent.
When the reaction is conducted at the preferred elevated
temperatures as described above, even the higher molecular weight
diamines will generally be in liquid state. A solvent such as
toluene, or p-xylene can be incorporated into the reaction mixture,
but the solvent must be removed after the reaction is completed,
which can be accomplished by distillation or simple vacuum removal.
The reaction is preferably conducted under an inert atmosphere such
as nitrogen and in the presence of a catalyst such as 0.1 weight
percent methyl acetate and 0.001 weight percent zinc powder. The
reaction is allowed to proceed to completion, usually not longer
than about 6 hours.
[0046] The lubricants formed by condensation reactions are a
mixture of amides characterized as having a melting range rather
than a melting point. As those skilled in the art will recognize,
the reaction product is generally a mixture of moieties whose
molecular weights, and therefore properties dependent on such, will
vary. The reaction product can generally be characterized as a
mixture of diamides, monoamides, bisamides, and polyamides. The
preferred amide product has at least about 50%, more preferably at
least about 65%, and most preferably at least about 75%, by weight
diamide compounds. The preferred amide product mixture contains
primarily saturated diamides having from 6 to 10 carbon atoms and a
corresponding weight average molecular weight range of from 144 to
200. A preferred diamide product is N,N'-bis{2-[(1
-oxooctadecyl)amino]ethyl}diamide.
[0047] The reaction product, containing a mixture of amide
moieties, is well suited as a lubricant in conventional
warm-pressing applications. The presence of monoamides allows the
lubricant to act as a liquid lubricant at the pressing conditions,
while the diamide and higher melting species act as both liquid and
solid lubricants at these conditions.
[0048] As a whole, the amide lubricant begins to melt at a
temperature between about 150.degree. C. (300.degree. F.) and
260.degree. C. (500.degree. F.), preferably about 200.degree. C.
(400.degree. F.) to about 200.degree. C. (500.degree. F.). The
amide product will generally be fully melted at a temperature about
250 degrees Centigrade above this initial melting temperature,
although it is preferred that the amide reaction product melt over
a range of no more than about 100 degrees Centigrade.
[0049] A preferred amide reaction product mixture has an acid value
of from about 2.5 to about 5; a total amine value of from about 5
to 15, a density of about 1.02 at 25.degree. C., a flash point of
about 285.degree. C. (545.degree. F.), and is insoluble in
water.
[0050] Amide lubricants are commercially available from Morton
International of Cincinnati, Ohio as ADVAWAX7 450 or PROMOLD 450,
which are each ethylene bis-stearamides having an initial melting
point between about 200.degree. C. and 300.degree. C. Other
ethylene bis-stearamide containing lubricants are available under
the tradename KENOLUBE from Hoganas Corporation, located in
Hoganas, AG Sweden. The KENOLUBE lubricant is a polymer material
containing a mixture of ethylene bisstearamide and zinc
stearate.
[0051] The amide lubricant will generally be added to the
composition in the form of solid particles. The particle size of
the lubricant can vary, but is preferably below about 100 microns.
Most preferably the lubricant particles have a weight average
particle size of about 5-50 microns.
[0052] Particulate internal lubricants are admixed with the
metal-based powder in an amount up to about 3 percent by weight of
the metallurgical powder composition. Preferably the metallurgical
powder composition is composed of from about 0.1 to about 2 weight
percent, more preferably about 0.1-1.0 weight percent, and even
more preferably about 0.2-0.5 weight percent, of particulate
internal lubricant. Even more preferably the metallurgical powder
composition is composed of from about 0.2 to about 0.4 weight
percent of particulate internal lubricant.
[0053] The metallurgical powder composition may also optionally
contain one or more binding agents, particularly where an
additional, separate alloying powder is used, to bond the different
components present in the metallurgical powder composition so as to
inhibit segregation and to reduce dusting. By "bond" as used
herein, it is meant any physical or chemical method that
facilitates adhesion of the components of the metallurgical powder
composition.
[0054] In one embodiment, bonding is carried out through the use of
at least one binding agent. Binding agents that can be used in the
present invention are those commonly employed by the powder
metallurgy industry. For example, such binding agents include those
found in U.S. Pat. No. 4,834,800 to Semel, U.S. Pat. No. 4,483,905
to Engstrom, U.S. Pat. No. 5,298,055 to Semel et.al., and U.S. Pat.
No. 5,368,630 to Luk, the disclosures of which are each hereby
incorporated by reference in their entireties.
[0055] Binding agents include, for example, polyglycols such as
polyethylene glycol or polypropylene glycol; glycerine; polyvinyl
alcohol; homopolymers or copolymers of vinyl acetate; cellulosic
ester or ether resins; methacrylate polymers or copolymers; alkyd
resins; polyurethane resins; polyester resins; or combinations
thereof. Other examples of binding agents that are useful are the
relatively high molecular weight polyalkylene oxide-based
compositions, e.g., the binders described in U.S. Pat. No.
5,298,055 to Semel et al. Useful binding agents also include the
dibasic organic acid, such as azelaic acid, and one or more polar
components such as polyethers (liquid or solid) and acrylic resins
as disclosed in U.S. Pat. No. 5,290,336 to Luk, which is
incorporated herein by reference in its entirety. The binding
agents in the '336 Patent to Luk can also act advantageously as a
combination of binder and lubricant. Additional useful binding
agents include the cellulose ester resins, hydroxy alkylcellulose
resins, and thermoplastic phenolic resins, e.g., the binders
described in U.S. Pat. No. 5,368,630 to Luk.
[0056] The binding agent can further be the low melting, solid
polymers or waxes, e.g., a polymer or wax having a softening
temperature of below 200.degree. C. (390.degree. F.), such as
polyesters, polyethylenes, epoxies, urethanes, paraffins, ethylene
bisstearamides, and cotton seed waxes, and also polyolefins with
weight average molecular weights below 3,000, and hydrogenated
vegetable oils that are C.sub.14-24 alkyl moiety triglycerides and
derivatives thereof, including hydrogenated derivatives, e.g.
cottonseed oil, soybean oil, jojoba oil, and blends thereof, as
described in WO 99/20689, published Apr. 29, 1999, which is hereby
incorporated by reference in its entirety herein. These binding
agents can be applied by the dry bonding techniques discussed in
that application and in the general amounts set forth above for
binding agents. Further binding agents that can be used in the
present invention are polyvinyl pyrrolidone as disclosed in U.S.
Pat. No. 5,069,714, which is incorporated herein in its entirety by
reference, or tall oil esters.
[0057] The amount of binding agent present in the metallurgical
powder composition depends on such factors as the density, particle
size distribution and amounts of the iron-alloy powder, the iron
powder and optional alloying powder in the metallurgical powder
composition. Generally, the binding agent will be added in an
amount of at least about 0.005 weight percent, more preferably from
about 0.005 weight percent to about 1.0 weight percent, and most
preferably from about 0.05 weight percent to about 0.5 weight
percent, based on the total weight of the metallurgical powder
composition.
[0058] Metallurgical powder compositions are easily removed from
compaction dies while still having low organic material content,
e.g., lubricant and binders. Metallurgical powder compositions
generally include from about 0.01 to about 2.0 weight percent,
preferably 0.01 to 1.0 weight percent of total organic material.
Preferably, metallurgical powder composition include from about 0.1
to about 0.5 weight percent, and more preferably from about 0.2 to
about 0.5 weight percent total organic material. Even more
preferably, metallurgical powder composition include about 0.4
weight percent total organic material.
[0059] In one embodiment, a metallurgical powder composition is
composed of a base metal powder and a particulate internal
lubricant containing an amide lubricant. Preferably, metallurgical
powder composition is composed of 0.40 weight percent of a
particulate internal lubricant. Preferably, the amide-containing
lubricant is composed of ethylene bis-stearamide having an initial
melting point between about 200.degree. C. and 300.degree. C. More
preferably, the amide-containing lubricant is composed of about
0.20 weight percent of a polyamide lubricant composed of ethylene
bis-stearamides having an initial melting point between about
200.degree. C. and 300.degree. C., e.g., Promold 450, and about
0.20 weight percent of a polyamide lubricant composed of an
ethylene bisstearamide and zinc stearate admixture, e.g.,
Kenolube.
[0060] In another embodiment, a metallurgical powder composition is
composed of a base metal powder bonded with a particulate internal
lubricant containing an amide lubricant. Preferably, the
metallurgical powder composition is composed of 0.40 weight percent
total organic content. The organics materials include 0.10 weight
percent binding agent and 0.30 weight percent internal lubricant
containing an amide lubricant. Preferably, the amide-containing
lubricant is composed of ethylene bis-stearamide having an initial
melting point between about 200.degree. C. and 300.degree. C. More
preferably, the amide-containing lubricant is composed of about
0.15 weight percent of a polyamide lubricant composed of ethylene
bis-stearamides having an initial melting point between about
200.degree. C. and 300.degree. C., e.g., Promold 450, and about
0.15 weight percent of a polyamide lubricant composed of an
ethylene bisstearamide and zinc stearate admixture, e.g., Kenolube.
Preferably, the binding agent among those found in U.S. Pat. No.
5,298,055 to Semel et.al.
[0061] Compacted articles prepared from metallurgical powder
compositions have high density. Preferably, compacted articles have
a density of at least about 6.6 g/cm.sup.3. More preferably,
compacted articles exhibit a density of at least about 7.2
g/cm.sup.3. More preferably compacted articles exhibit a density of
from about 7.25 g/cm.sup.3 to about 7.7 g/cm.sup.3. Even more
preferably, compacted articles exhibit a density of from about 7.35
g/cm.sup.3 to about 7.6 g/cm.sup.3. Still more preferably,
compacted articles exhibit a density of from about 7.4 g/cm.sup.3
to about 7.6 g/cm.sup.3. More preferably, the compacted articles
exhibit a density greater than 7.45 g/cm.sup.3.
[0062] Methods for preparing metallurgical powder compositions are
"one step" methods or "multi step" methods. A "one step" method
includes of a first step of admixing a base metal powder, metal
phosphate, a particulate internal lubricant, and optional alloying
powders, and additives that will form the metallurgical powder
composition. Generally, the base-metal powder, optional alloying
powder, and particulate internal lubricant (along with any other
conventional additive) are admixed, preferably in dry form, by
conventional mixing techniques, such as the use of a double cone
blender, to form a substantially homogeneous particle blend. The
admixture is then combined with protonic acid to react and form a
metal phosphate coating on the component powders. In one
embodiment, the metal phosphate layer is formed at the same time
that the particles are being bonded together with a binding agent.
The "one step" process saves time and related expense in
manufacturing processes, especially large scale processes for
fabricating commercial quantities of metallurgical powder
compositions.
[0063] A "multi step" method includes forming a metal phosphate
coating on a metal based powder prior to admixing with a
particulate internal lubricant and optional additives that will
form the metallurgical powder composition. First, a base-metal
powders, optionally alloying powders, or combination of both, are
admixed with a metal phosphate. The admixture is then combined with
a protonic acid to react to form a metal phosphate coating on the
admixture of powders. The coated admixture is then combined with a
particulate internal lubricant and any additional optional alloying
powders or additives, e.g., binders. Generally, the "multi step"
process provides a greater increase in lubricity and green strength
over conventional techniques compared to the "one step"
process.
[0064] Protonic acids are any substance that can donate a hydrogen
ion (proton). Exemplary protonic acids include, for example, but
are not limited to, hydrochloric acid, nitric acid, sulfuric acid,
acetic acid, phosphoric acid, and water. Preferably, the protonic
acid is phosphoric acid, hydrochloric acid, sulfuric acid, or
nitric acid. More preferably, the protonic acid is phosphoric
acid.
[0065] Optionally, the protonic acid may be diluted in a solvent
prior to being combined with the admixture of base-metal powder and
metal phosphate. Typical solvents include, for example, acetone,
ethyl acetate, water, diethyl ether, dichloromethane, methanol,
ethanol, and toluene. Preferably, the solvent is acetone. The
solvent is removed from the admixture via conventional drying
techniques, such as for example, vacuum techniques, heating the
admixture to from about 100.degree. F. to about 150.degree. F., or
combinations thereof.
[0066] Optionally, the base-metal powder and metal phosphate are
heated prior to addition of the protonic acid. The admixture of
base-metal powder and metal phosphate is heated to at least about
100.degree. F., more preferably, from about 100.degree. F. to about
125.degree. F., and even more preferably at about 110.degree.
F.
[0067] Optionally, after the protonic acid and metal phosphate have
reacted with the base metal powder, the protonic acid is not
removed so that the metallurgical powder compositions may include a
small amount of excess protonic acid, such as for example from
about 0.001 to about 0.2 weight percent of protonic acid.
[0068] In some embodiments, metallurgical powder compositions are
prepared by first admixing and bonding a base metal powder, metal
phosphate, optional alloying powders, and a polyamide lubricant
composed of ethylene bis-stearamides having an initial melting
point between about 200.degree. C. and 300.degree. C., e.g.,
Promold 450, and a lithium stearate or a polyamide lubricant
composed of an ethylene bisstearamide and zinc stearate admixture,
e.g., Kenolube. The composition is then reacted with phosphoric
acid until completion and the metallurgical powder composition is
dried, preferably in air. The composition is then admixed with
additional lithium stearate or Kenolube.
[0069] Methods of prepared compacted articles include a first step
of providing a metallurgical powder composition. The metallurgical
powder composition is placed in a compaction die cavity and
compacted under pressure, such as between about 5 and about 200
tons per square inch (tsi), more commonly between about 10 and 100
tsi, and even more commonly between about 30 and 60 tsi. The
compacted part is then ejected from the die cavity. The die may
optionally be cooled below room temperature or heated above room
temperature. The die may be heated to greater than about
100.degree. F. Preferably the die is heated to greater than about
120.degree. F. More preferably, the die is heated to as much as
270.degree. F., such as for example from about 150.degree. F. to
about 500.degree. F.
[0070] Optionally, an external lubricant can be applied to the die
wall. External lubricants include graphite, boron nitride, and
ethylene bisteramide, including high temperature variants of the
same. Preferably the external lubricant is boron nitride.
[0071] The amount of external lubricant applied to a die wall is
typically from about 0.0 to about 2.0 weight percent, preferably
0.01 to 0.5 weight percent of the metallurgical powder composition.
Preferably, from about 0.01 to about 0.25 weight percent, and more
preferably from 0.01 to about 0.15 weight percent particulate
internal lubricant is applied to the die wall. Generally, when
metallurgical powder compositions include at least 0.4 weight
percent particulate internal lubricant, an external lubricant is
not use. In some embodiments, however, an external lubricant is
used when preparing compacts with metallurgical powder compositions
composed of at least 0.4 weight percent particulate internal
lubricant.
[0072] The compacted ("green") part may be optionally sintered to
enhance its strength. The compacted part is sintered using
conventional sintering techniques known to those skilled in the
art. Sintering is conducted for a time and at a temperature
sufficient to achieve metallurgical bonding and alloying.
Additional processes such as forging or other appropriate
manufacturing technique or secondary operation may be used to
produce a finished part.
[0073] Sintering is advantageously conducted at a temperature of at
least 2050.degree. F. (1200.degree. C.), preferably at least
2150.degree. F. (1175.degree. C.), more preferably at least about
2200.degree. F. (1200.degree. C.), more preferably at least about
2250.degree. F. (1230.degree. C.), and even more preferably at
least about 2300.degree. F. (1260.degree. C.).
[0074] Those skilled in the art will appreciate that numerous
changes and modifications may be made to the preferred embodiments
of the invention and that such changes and modifications may be
made without departing from the spirit of the invention. The
following examples further describe the metallurgical powder
compositions.
EXAMPLES
[0075] Some embodiments of the present invention will be described
in detail in the following Examples. Base-metal powder composition
were prepared and formed into compacted parts in accordance with
the methods described above. The compacted parts were evaluated for
green and sintered properties. The forces necessary to remove the
compacted parts from a compacting die were also evaluated. Lastly,
the bonding properties of zinc phosphate were analyzed.
Example 1
[0076] Metallurgical powder compositions were prepared to analyze
green and sintered properties. Composition 1 was prepared by
combining a prealloyed iron based powder composed of 0.85 weight
percent molybdenum and balance iron, 0.1 weight percent zinc
phosphate, 0.1 weight percent phosphoric acid, 2.0 weight percent
nickel, 0.6 weight percent graphite, and 0.5 weight percent
particulate internal lubricant. The prealloyed iron based powders
in Compositions 1 & 2 are commercially available as Ancorsteel
A85HP from Hoeganaes Corp. in Cinnaminson, N.J. The particulate
internal lubricants in Compositions 1 & 2 are commercially
available as Acrawax from Glycol Chemical Co.
[0077] Composition 2 was prepared by combining a prealloyed iron
based powder composed of 0.85 weight percent molybdenum and balance
iron, 2.0 weight percent nickel, 0.6 weight percent graphite, and
0.6 weight percent particulate internal lubricant.
[0078] Compositions 1 & 2 were compacted at 50 tons per square
inch (tsi) to form test bars. Green properties of the test bars
were evaluated. Green density was evaluated using ASTM B331-95 test
methodology. Green strength was evaluating using ASTM B312-96 test
methodology. Green expansion was determined according to the
following equation: Green .times. .times. Expansion .times. .times.
( % ) = 100 .times. [ ( Green .times. .times. bar .times. .times.
length ) - ( Die .times. .times. length ) ] Die .times. .times.
length ##EQU1##
[0079] The results are reported below in Table 1: TABLE-US-00001
TABLE 1 Green Compaction Density Green Strength Green Sample Temp.
(.degree. F.) (g/cm.sup.3) (psi) Expansion (%) Composition 1 Room
Temp. 7.19 2144 0.28 Composition 2 Room Temp. 7.19 2271 0.28
Composition 1 145 7.24 4270 0.23 Composition 2 145 7.24 2620 0.25
Composition 1 200 7.31 6547 0.20 Composition 2 200 7.30 2777 0.24
Composition 1 270 7.39 6614 0.21 Composition 2 270 7.38 3050
0.24
[0080] Green compacts made from metallurgical powder compositions
containing a metal phosphate coating exhibited improved
compressibility, higher green strength, and lower green expansion
compared to green compacts made from compositions that did not
include a metal phosphate coating. As shown in Table 1, the green
strength of composition 1 was higher than the green strength of
composition 2 at compaction temperatures greater than 120.degree.
F. Similarly, the green expansion of composition 1 was lower than
the green expansion of composition 2.
[0081] The ejection forces necessary to remove the compacted part
from the die were analyzed. Strip pressure measures the static
friction that must be overcome to initiate ejection of a compacted
part from a die. It was calculated as the quotient of the load
needed to start the ejection over the cross-sectional area of the
part that is in contact with the die surface, and is reported in
units of psi. Slide pressure is a measure of the kinetic friction
that must be overcome to continue the ejection of the part from the
die cavity; it is calculated as the quotient of the average load
observed as the part traverses the distance from the point of
compaction to the mouth of the die, divided by the surface area of
the part, and is reported in units of psi. The results are reported
below in Table 2: TABLE-US-00002 TABLE 2 Compaction Green Density
Sample Temp. (.degree. F.) (g/cm.sup.3) Strip (psi) Slide (psi)
Composition 1 Room Temp. 7.19 3315 2171 Composition 2 Room Temp.
7.19 4191 2432 Composition 1 145 7.24 4023 2093 Composition 2 145
7.24 4523 2425 Composition 1 200 7.31 3891 2012 Composition 2 200
7.30 4382 2452 Composition 1 270 7.39 3087 2213 Composition 2 270
7.38 2833 1804
[0082] At low compaction temperature green compacts made from
metallurgical powder compositions containing a metal phosphate
coating were removed from the die by lower ejection forces compared
to the ejection forces required to remove green compacts prepared
from compositions that did not include a metal phosphate coating.
As shown in Table 2, at compaction temperatures below 270.degree.
F., composition 1 required lower ejection forces to remove the
green compact from a die compared the ejection forces required to
remove a compact prepared from composition 2.
[0083] The compacted parts were sintered at 2050.degree. F. for
about 20 minutes. Sintered properties of the test bars were
evaluated. The results are reported below in Table 3:
TABLE-US-00003 TABLE 3 Compaction Sintered Temp. Density DC TRS
Hardness Sample (.degree. F.) (g/cm.sup.3) (%) (ksi) (Hra)
Composition 1 Room Temp. 7.21 0.18 191 56.9 Composition 2 Room
Temp. 7.21 0.13 193 56.3 Composition 1 145 7.25 0.18 196 57.0
Composition 2 145 7.25 0.15 203 56.5 Composition 1 200 7.29 0.18
202 56.8 Composition 2 200 7.30 0.16 211 57.6 Composition 1 270
7.36 0.18 217 57.9 Composition 2 270 7.35 0.19 224 58.0
Example 2
[0084] Pilot scale production powder blends were prepared to
analyze the bonding properties of metallurgical powder
compositions. Composition 3 was prepared by combining a
substantially pure iron powder, an Fe--Cr--Si masteralloy powder,
graphite, and a particulate internal lubricant. The blend of
substantially pure iron powder and Fe--Cr--Si masteralloy powder is
commercially available as A4300 from Hoeganaes Corp. The Fe--Cr--Si
masteralloy powder was of the type described in U.S. patent
application Ser. No. 10/818,782, which is herein incorporated by
reference in its entirety. The blended metallurgical powder
composition was composed of 1.0 weight percent chromium, 1.0 weight
percent nickel, 0.8 weight percent molybdenum, 0.6 weight percent
silicon, 0.1 weight percent manganese, 0.6 weight percent graphite,
and 0.75 weight percent particulate internal lubricant (Acrawax).
Composition 3 did not contain zinc phosphate coated powders.
[0085] Composition 4 was prepared using the bonding process
described in U.S. Pat. No. 5,290,336. This metallurgical powder
composition was composed of 0.55 weight percent of particulate
internal lubricant (Acrawax). This composition illustrates the
retention characteristics imparted to powder compositions that have
been bonded using conventional bonding techniques.
[0086] Composition 5 was prepared by combining a prealloyed iron
based powder, an Fe--Cr--Si masteralloy powder, a nickel powder,
graphite, and a particulate internal lubricant. The prealloyed iron
based powder was composed of 0.85 weight percent molybdenum and
balance iron, which is commercially available as Ancorsteel A85HP
from Hoeganaes Corp. The prealloyed iron based powder was coated
with 0.1 weight percent zinc phosphate. The Fe--Cr--Si masteralloy
powder was of the type used in Composition 3. The blended
metallurgical powder composition was composed of 1.0 weight percent
chromium, 1.0 weight percent nickel, 0.8 weight percent molybdenum,
0.6 weight percent silicon, and 0.4 weight percent particulate
internal lubricant (Acrawax).
[0087] Composition 6 was prepared by combining the components of
Composition 5, except that each of the prealloyed iron based
powder, the Fe--Cr--Si masteralloy powder, and the nickel powder
was coated with 0.1 weight percent zinc phosphate, based on the
weight of the metallurgical powder composition.
[0088] Composition 7 was prepared by combining a prealloyed iron
based powder, an Fe--Cr--Si masteralloy powder, a nickel powder,
graphite, a particulate internal lubricant, and an external
lubricant. The prealloyed iron based powder, the Fe--Cr--Si
masteralloy powder, and the nickel powder were each coated with 0.1
weight percent of zinc phosphate, based on the weight of the
metallurgical powder composition. Composition 7 was bonded by using
conventional bonding techniques described in U.S. Pat. No.
5,290,336. The blended metallurgical powder composition was
composed of 1.0 weight percent chromium, 1.0 weight percent nickel,
0.8 weight percent molybdenum, 0.6 weight percent silicon, 0.2
weight percent particulate internal lubricant (Acrawax), and 0.2
weight percent of an external lubricant.
[0089] Bonding properties were analyzed by examining the
composition's susceptibility to "dusting" effects. "Retention" is
defined as the amount of fine powder additives retained within the
powder mass after it is subjected to a pulsating air pressure.
Retention is measured by subjecting a fixed amount of powder to a
pulsating stream of air pressure in an open top vessel. The
pulsating air pressure will cause both fine metal powders and
low-density additives, such as for example graphite and lubricant,
to separate from the powder mass and float out of the containing
vessel according to Stokes Law. The amount of fine powder or
low-density additive remaining in the powder is measured by
collecting the separated powder, weighing, and then determining the
amount retained. The retention data for compositions 3-7 is
described in Table 4: TABLE-US-00004 TABLE 4 Retention: Master
Retention: Phosphate Alloy Nickel Sample Coating Bonded Powder
Powder Composition 3 No No 31% 24% Composition 4 No Yes 80% 67%
Composition 5 Only Iron No 37% 24% Prealloy Powder Composition 6
Iron Prealloy Powder, No 76% 68% Master Alloy Powder, Nickel Powder
Composition 7 Iron Prealloy Powder, Yes 90% 87% Master Alloy
Powder, Nickel Powder
[0090] As shown in Table 4, a non-bonded material will retain about
31% of the master alloy and 24% of the fine nickel additive.
Conventional bonding processes increases these amounts to 80% and
67% respectively. Phosphate treating the iron powder and then
adding the master alloy and nickel and premix additives does not
substantially increase the amount of alloy retained. However,
adding the master alloy and nickel and then phosphate coating the
iron powder results in a significant increase in the amount of
additives retained within the powder mass, similar to what is
achieved with conventional bonding processes. If this same material
is then subjected to an conventional bonding processes, the amount
of powder retained exceeds what can be achieved by the conventional
bonding process or metal phosphate treatment alone.
Example 3
[0091] Pilot scale production powder blends were prepared to
analyze the physical properties of metallurgical powder
compositions. Composition 8 was a metallurgical powder composition
prepared by combining a prealloyed iron powder with nickel powder,
graphite, and particulate internal lubricant. The metallurgical
powder composition included 0.85 molybdenum, 2.0 weight percent
nickel, 0.4 weight percent graphite, 0.1 weight percent zinc
phosphate, and 0.4 weight percent lithium stearate particulate
internal lubricant. The prealloyed iron based powder was composed
of 0.85 weight percent molybdenum and balance iron (Ancorsteel
A85HP). The particulate internal lubricant was commercially
available from Lonza Corp. in New Jersey.
[0092] Composition 8 was compacted into test bars on a conventional
mechanical compacting press at 150.degree. F. and 53 tons per
square inch. The test bars exhibited a green density of 7.4
g/cm.sup.3. The green compact was then sintered at 2050.degree. F.
for about 20 minutes. The sintered compact exhibited a density of
7.47 g/cm.sup.3.
[0093] Composition 8 was compared to a conventional metallurgical
powder compositions composed of 0.55% total organic material. This
composition is commercially available as AncorMaxD from Hoeganaes
Corp. Both powders were compacted at 50 tsi and die temperatures
greater than 150 F. The conventional composition exhibited a green
density of about 7.30 to 7.35 g/cm.sup.3. Composition 8 utilizes
only 0.40% total organic content and exhibited a green density of
about 7.37 to 7.42 g/cm.sup.3.
[0094] Composition 9 was a metallurgical powder composition
prepared by combining a diffusion bonded powder coated with zinc
phosphate, graphite, and an particulate internal lubricant. The
diffusion bonded powder was composed of about 4.05% nickel, about
0.55% molybdenum, and about 1.6% copper. The diffusion bonded
powder is commercially available as DISTALOY 4800A from Hoeganaes
Corporation. Composition 9 was composed of 0.4 weight percent
graphite, 0.1 weight percent zinc phosphate, and 0.2 weight percent
particulate internal lubricant. The particulate internal lubricant
is produced by Hoeganaes Corporation of Riverton, N.J. as
Promold.TM. 450.
[0095] Composition 9 was compacted into test bars on a conventional
mechanical compacting press at 450.degree. F. and 50 tons per
square inch. The test bars exhibited a green density of .about.7.45
g/cm.sup.3 and a sintered density of .about.7.5 g/cm.sup.3. This
composition exhibited green strengths in excess of 11,000 psi.
Moreover, sintered mechanical properties were unaffected by the
addition of zinc phosphate.
Example 4
[0096] Compacted parts were prepared to examine the ejection forces
required to remove the parts from a die. Composition 10 was a
metallurgical powder composition prepared by bonding a prealloyed
iron based powder with an graphite and an internal lubricant
containing an amide lubricant. The prealloyed iron based powder was
composed of 0.85 weight percent molybdenum and balance iron that
was combined with 0.1 weight percent zinc phosphate, 0.1 weight
percent phosphoric acid, 0.6 weight percent graphite, and 0.4
weight percent total organic content. The prealloyed iron based
powder is commercially available as Ancorsteel A85HP from Hoeganaes
Corp. in Cinnaminson, N.J. The organic materials included 0.10
weight percent binding agent and 0.30 weight percent particulate
internal lubricant containing an amide lubricant. The particulate
internal lubricant was composed of about 0.15 weight percent of a
polyamide lubricant commercially available as KENOLUBE from Hoganas
Corporation, located in Hoganas, AG Sweden, and about 0.15 weight
percent of a polyamide lubricant commercially available as PROMOLD
450 from Morton International of Cincinnati, Ohio.
[0097] Composition 11 was a metallurgical powder composition
prepared by admixing a prealloyed iron based powder with 0.6 weight
percent graphite and 0.4 weight percent particulate internal
lubricant. The prealloyed iron based powder was composed of 0.85
weight percent molybdenum and balance iron. The particulate
internal lubricant was commercially available as Acrawax from
Glycol Chemical Co.
[0098] Composition 12 was a metallurgical powder composition
prepared in the same manner as Composition 11, except that the 0.4
weight percent particulate internal lubricant was replaced with
0.75 weight percent of Acrawax particulate lubricant.
[0099] Compositions 10, 11, and 12 were compacted at 30, 40, 50,
and 60 tons per square inch (tsi) to form test bars measuring one
inch tall and 0.56 inches in diameter. Ejection properties of the
test bars were evaluated.
[0100] FIG. 1 is a graph of ejection pressure verses time for test
bars prepared from composition 10. FIGS. 2 and 3 are graphs of
ejection pressure verses time comparing test bars prepared from
compositions 10, 11, and 12. Test bars prepared from compositions
11 and 12 were heavily scored at 40 tsi and could not be produced
when compressed at 50 and 60 tsi. Referring to FIGS. 1 and 2, bars
prepared from composition 10 required lower strip and slide forces
for removal from a die compared with bars prepared from
compositions 11 and 12. Thus, it was easier to remove bars prepared
from composition 10 compared to bar prepared from compositions 11
and 12.
[0101] One method of evaluating compacted parts is to compare the
ratio of die surface area to planer area, i.e. M/Q ratio. Shown
below in table 5 are calculated M/Q ratios for various die
configurations: TABLE-US-00005 TABLE 5 Cincy bushing HC Gear Cincy
bushing HC Gear GS Bar ToniTek Slug 1.5 OD, 1.0 ID 16 teeth 1.5 OD,
1.0 ID 16 teeth 0.5'' .times. 1.25'' 0.55'' diameter Height core
rod surface (core rod surface (core rod not (Inches) (area
included) area excluded) applicable) 0.250 2.0 3.0 1.2 2.5 1.4 1.8
0.375 3.0 4.5 1.8 3.8 2.1 2.7 0.500 4.0 6.0 2.4 5.1 2.8 3.6 0.625
5.0 7.5 3.0 6.4 3.5 4.5 0.750 6.0 9.0 3.6 7.6 4.2 5.5 0.875 7.0
10.5 4.2 8.9 4.9 6.4 1.000 8.0 12.0 4.8 10.2 5.6 7.3 1.125 9.0 13.5
5.4 11.5 6.3 8.2 1.250 10.0 15.0 6.0 12.7 7.0 9.1 1.375 11.0 16.5
6.6 14.0 7.7 10.0 1.500 12.0 18.0 7.2 15.3 8.4 10.9 1.625 13.0 19.5
7.8 16.5 9.1 11.8 1.750 14.0 21.0 8.4 17.8 9.8 12.7 1.875 15.0 22.5
9.0 19.1 10.5 13.6 2.000 16.0 24.0 9.6 20.4 11.2 14.5
[0102] M/Q ratios were useful for comparing the ejection properties
of known geometric slugs and more complex parts. Generally,
ejection forces required to remove parts from a die were similar
between parts having similar M/Q values. For example with reference
to Table 5, the ejection force required to remove a 0.55' diameter
Tonitec slug having a height of 1.0' (M/Q =7.3) from a die was
similar to the ejection force needed to remove a 16 tooth HC gear
of 0.625 inch height for example (MIQ=7.5).
* * * * *