CA 02642254 2008-08-12
DESCRIPTION
IRON-BASED POWDER MIXTURE, AND METHOD OF MANUFACTURING
IRON-BASED COMPACTED BODY AND IRON-BASED SINTERED BODY
Technical Field
The present invention relates to an iron-based powder
mixture including iron-based power mixed with a lubricant, and
alloying powder as needed. The iron-based powder mixture of
the invention is suitable for powder metallurgy, and
particularly suitable for compaction in a temperature range
from normal temperature to less than 10000.
The invention further relates to a powder mixture for
powder metallurgy, which is preferable for manufacturing of
high-strength sintered parts for automobiles.
Moreover, the invention relates to a method of
manufacturing an iron-based compacted body using the
iron-based powder mixture as a material, and a method of
manufacturing an iron-based power sintered-body using the
iron-based compacted body as a material.
Background Art
The iron-based powder mixture for powder metallurgy is
typically manufactured in a way that iron-based powder is added
with a lubricant and alloying powder and mixed, and furthermore
added with powder of free machining additives and mixed as
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needed.
Here, the iron-based powder is a main component of the
powder mixture, andiron powder (including pure iron powder),
or alloyed steel powder is mainly used as the iron-based powder.
The alloyed steel powder contains an alloyed element. While
steel powder containing no C may be used as the alloyed steel
powder, steel powder containing C and iron powder containing
no C are generally called alloyed. steel powder herein. In
addition to the above, partly diffused alloyed steel powder
may be used, in which an alloy element is bonded to pure iron
powder or the like by partial diffusion. In the application,
the partly diffused alloyed steel powder is assumed to be a
type of the alloyed iron powder.
The lubricant is an additive that is added particularly
for facilitating compaction or ejection of a compacted body
from a die after compaction. While various substances can be
used for the lubricant, the lubricant is selected in
consideration of a mixing property with iron-based powder or
a decomposition property during sintering. As an example of
the lubricant, zinc stearate, aluminum stearate, lead stearate
and the like are listed. Various lubricants are exemplified
in US Patent No.5,256,185 and the like.
The alloying powder is added mainly for adjusting a
composition and/or a structure of an iron-based compacted body
or an iron-based sintered body, and includes graphite powder,
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copper powder, iron phosphide powder, molybdenum powder, and
nickel powder.
The powder of free machining additives (or free machining
elements), such as S or MnS , is added particularly for improving
machining performance of the sintered body.
Recently, with increase in demand for increasing
strength of sintered parts, as disclosed in Japanese Unexamined
Patent Application Publication JP-A-2-156002 (1990), Japanese
Examined Patent Application Publication JP-B-7-103404 (1995),
and US Patent No.5,368,630, a warm compaction technique has
been developed, in which an iron-based powder mixture is
compacted while being heated, thereby increase in density and
increase in strendth of a compacted body can be achieved.
According to the technique, density of a compacted body can
be increased at a relatively low load by using a phenomenon
that iron-based powder is gradually reduced in resistance to
plastic deformation as the powder is heated.
However, such an iron-based powder mixture has the
following problems. That is, the warm compaction is a
.technique that a die and powder are heated to high temperature
beforehand, then the iron-based powder mixture is compacted.
As the heating temperature, while a range of 70 to 120 C is
described in JP-A-2-156002, heating is substantially
preferably performed at 100 C or more as described in
JP-B-7-103404 and USP 5,368,630. However, since it is very
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S.
difficult that the iron-based powder Mixture having low heat
conductivity is uniformly heated to 100 C or more, and kept
at the temperature, productivity of sintered parts have been
likely reduced. Moreover, the iron-based powder mixture is
heated for a long time, resulting in a .problVa,...:Ht.hat the
iron-based powder mixture is oxidized.
JP-A-9-104901 (1997) or JP-A-10-31.7001 (1998) discloses
a technique that an inorganic compound having a layered crystal
such as M0S2, carbon fluoride, and graphite is used as the
lubricant. However, when MoS2 is used, the MoS2 may .be
decomposed during sintering, causing generation of harmful
sulfur gas that possibly contaminates a furnace. When carbon
fluoride is used So that the iron-based powder mixture is .
sintered in a hydrogen atmosphere, there is fear that corrosive
hydrogen fluoride may be generated.
Therefore, it is desired to develop an iron-based powder
mixture having high compressibility similar to that of a
warm-compacted, iron-based powder mixture, even if it is
not subjected to warm compaction.
On the other hand, for the iron-based powder mixture,.
the problem of machining performance is also desired to be
solved.
When parts of various machines such as automobiles are
manufactured by a powder metallurgy technique, a powder mixture
for powder metallurgy is filled in a die and compacted, and
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furthermore sintered. Parts of various machines obtained in
this way (hereinafter, called sintered parts) typically have
a density of 5.0 to 7.2 g/cm3 respectively. Moreover, since
each of the sintered parts is good in dimension accuracy, a
part having a complicated shape can be produced.
The sintered parts are used for parts of various machines.
In particular, parts for automobiles (for example, gears) are
required to have high strength and high fatigue characteristics.
Thus, a technique of using a powder mixture for powder
metallurgy, which is added with an alloyed element, is
variously investigated in order to manufacture a sintered cart
having high strength and high fatigue characteristics. For
example, 5P-3-45-9649 (1970) discloses a powder mixture for
powder metallurgy, which includes cure Fe powder
diffusion-bonded with powder of Ni, Cu, Mo or the like, and
is preferable for manufacturing, a sintered cart having high
strength and high fatigue characteristics, and is excellent
in compressibility. Moreover, as a powder mixture for powder
metallurgy preferable for manufacturing a sintered cart having
high strength, JP-A-61-163239 (1986) discloses a powder
mixture for powder metallurgy, which includes low
alloyed-steel powder, in which C and Mc are contained, and Mn
and Cr are substantially not contained, the steel powder being
added with Cu powder and/or Ni powder, and furthermore, added
with graphite powder. Moreover, JP-A-63-114903 (1988)
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discloses a powder mixture for powder metallurgy, in which Cu
powder is diffusion-bonded to alloyed steel powder containing.
Mo, Mn and C.
However, even if powder metallurgy techniques are used,
when a sintered part, which is required to have extremely strict
dimension accuracy, is manufactured, the sintered part needs
to be subjected to machining (such as cutting or drilling) after
sintering. However, since a sintered part is bad in machining
performance, a cutting tool used in the machining is
significantly worn. As a result, machining cost is increased,
leading to increase in manufacturing cost of a sintered part.
Such degradation in machining performance of a sintered part
is caused by a phenomenon that a solid surface intermittently
appears in the inside of a work material due to pores within
the sintered part, which intermittently give a shock to a tool
during cutting, in addition, heat conductivity of the sintered
part is thus =decreased, and consequently temperature of the
sintered part is increased during cutting. The machining
performance is sidnificantly degraded as strength of a sintered
part is increased.
As described before, it is previously known that the
powder mixture for powder metallurgy is added with free
machining additives, thereby machining performance of a
sintered part is improved. The free machining additives have
an effect of easily breaking chips, or an effect of forming
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a thin built-up edge on a surface of a. cutting tool to improve
lubricity of the cutting tool (particularly, on a rake face).
However, free machining additives containing S as amain
component, like MoS2 described above, contaminate a furnace.
Moreover, in the techniques disclosed in JP-3-45-9649,
JP-A-61-163239, and JP-A-63-114903, since hardness of the
obtained sintered part is particularly high, even if the free
machining additives are added to the powder mixture for powder
metallurgy, significant improvement of machining performance
cannot be expected.
As a technique of eliminating a bad effect on the furnace
to improve machining performance of a sintered part, a
technique of using an MgO-S102 composite oxide is proposed.
For example, JP-A-1-255604 (1989) discloses a technique that
an MgO-Si02 composite oxide (for example, anhydrous talc), in
which MgO/Si02 is 0.5 or more and less than 1.-0 in mol ratio,
and crystallization water is not contained, is blended to
iron-based powder as means of improving machining performance
without reducing mechanical properties (for example,
strength) of a sintered body. Moreover, JP-A-64-79302 (1989)
discloses a technique that free machining additives including
a MgO-Si02 composite oxide and/or glass powder are contained
in reduced iron powder in a configuration that the additives
stay inside of each iron powder particle (that is, the additives
are added to iron powder raw material before reduction).
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Any of the publications describes that the composite
oxide is preferably added in a range of 0.1 to 1.5 wt%. However,
according to a result of investigation on iron-based powder
containing a lubricant (zinc stearate of 1 wt%) or the like,
as an added amount of the composite oxide is increased, an
effect of improving machining performance is increased, and
particularly large effect is obtained in a range of 0.5 to 1.0
wt%, but on the other hand, mechanical properties are reduced
(Table 3 in JP-A-1-255604, and Figs 6 and 8 in JP-A-64-79302).
That is, the techniques are not necessarily advantageous in
a point of quality of a sintered body.
Disclosure cf the inventon
Problems that the Invention is to Solve
The invention advantageously solves the problems, and
an object of the invention is to propose an iron-based powder
mixture for powder metallurgy, which has no adverse effect on
furnace environment during sintering a compact, and provides
excellent compaction performance that the powder mixture can
be compacted at high density even in a low temperature region
of less than 100 C.
Moreover, in consideration of increase in demand for
improving machining performance of a sintered part to reduce
machining cost, another object of the invention is to provide
an iron-based powder mixture for powder metallurgy preferable
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for machining a sintered part having excellent machining
performance, and particularly preferable for machining a
high-strength sintered part.
Still another object of the invention is to propose a
method of manufacturing an iron-based compacted body using the
iron-based powder mixture as a material, and furthermore, a
method of manufacturing an iron-based sintered body using the
iron-based compacted body as a material.
Means for Solving the Problems
As a measure for solving the problems, the inventors made
earnest investigations on a particular lubricant, by which when
an iron-based powder mixture is compacted, furnace environment
is not adversely affected, and even if the iron-based powder
mixture is compacted at a relatively low heating temperature
of the iron-based powder mixture, and preferably even if it
is compacted without being heated, a high-density compacted
body can be manufactured.
As a result, they had a finding that when talc or steatite
was used as a lubricant, and furthermore, fatty acid amide was
used, rearrangement of iron-based powder particles was
accelerated during compaction, consequently even if
compaction temperature was low, that is, about room temperature,
an iron-based compacted body having high compaction density
was obtained.
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Moreover, it was found that when metallic soap was added,
an extremely high effect of improving machining performance was
obtained by talc or steatite in a low added amount compared
with a previously known amount, which had no adverse influence
on mechanical properties.
The invention is designed on the above findings.
That is, summary and configuration of the invention are
as follows:
(1) An iron-based powder mixture containing an iron-
based powder, and containing as additives,
steatite powder, or talc powder and steatite powder in an
amount of 0.01 to 0.5 mass% in total mixed in the iron-based
powder mixture,
fatty acid amide as a binder in an amount of 0.01 to 0.5
mass% in total in the iron-based powder mixture, and
metallic soap in an amount of 0.01 to 0.5 mass% in the
iron-based powder mixture.
(2) The iron-based powder mixture according to the above
(1) wherein the iron-based powder mixture is further blended
with alloying powder.
(3) The iron-based powder mixture according to the above
(2) wherein the iron-based powder is water-atomized alloyed
steel powder containing Mo of 0.3 to 0.5 mass%, Mn of 0.1 to
0.25 mass%, and the remainder being Fe and inevitable
impurities, and
wherein the alloying powders are Cu powder of 1 to 3 mass%
and graphite powder of 0.5 to 1.0 mass% in the iron-based
powder mixture.
(4) An iron-based powder mixture, characterized in that:
the iron-based powder mixture is formed by mixing water-
atomized alloyed steel powder containing Mo of 0.3 to 0.5
mass%, Mn of 0.1 to 0.25 mass%, and the remainder being Fe and
Mk 02642254 2011-10-25
inevitable impurities, Cu powder of 1 to 3 mass% in the iron-
based powder mixture, graphite powder of 0.5 to 1.0 mass% in
the iron-based powder mixture, steatite, or talc and steatite
in a range of 0.05 to 0.5 mass% in total in the iron-based
powder mixture, fatty acid amide as a binder in an amount of
0.01 to 0.5 mass% in the iron-based powder mixture, and
metallic soap in an amount of 0.01 to 0.5 mass% in the iron-
based powder mixture.
(5) The iron-based powder mixture according to the above
(4)wherein the iron-based powder mixture further contains
metallic soap.
(6) A method of manufacturing an iron-based compacted
body, characterized in that: the iron-based powder mixture
according to the above (1) or (2) is filled in a die, then
compacted at a temperature of less than 100 C.
(V) A method of manufacturing an iron-based sintered
body, characterized in that: the iron-based powder mixture
according to the above (1) or (2) is filled in a die, then
compacted at a temperature of less than 100 C, and then an
obtained iron-based compacted body is sintered.
(8) The iron-based powder mixture according to any one
of the above (1) to (5) containing steatite, or talc and
steatite in a range of 0.05 to 0.3 mass% in total in the iron-
based powder mixture.
(9) The method according to the above (6) or (7)wherein
the iron-based powder mixture contains steatite, or talc and
steatite in a range of 0.05 to 0.3 mass% in total in the iron-
based powder mixture.
Each of the content of an alloyed element (including Mo
or Mn) in the iron-based powder, the amount of alloying powder
(including Cu powder and graphite powder) to be added, and the
added amount of talc or steatite refers to percentage of mass
of the iron-based powder mixture.
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Best mode for Carrying Out the Invention
Hereinafter, the invention is specifically described.
First, materials of the iron-based powder mixture of the
invention are described. The content of each of alloyed
elements in the iron-based powder, and the blending amount of
each of the materials (alloying powder, lubricant and the like)
are expressed in a weight percent of mass (100 mass%) of an
iron-based powder mixture obtained by mixing those, that is,
the weight percent is expressed using a numerical value
included in a numerical value of the mass of the powder mixture.
However, such a weight percent is not significantly different
in numerical value from that in the case that the alloy content
(including the amount of partly diffused alloy) and the like
in the iron-based powder is expressed in a weight percent of
=
mass of the iron-based powder.
<Iron-based powder>
In the invention, as the iron-based powder, pure iron
powder such as atomized iron powder or reduced iron powder,
or alloyed steel powder is exemplified. As the alloyed steel
powder, partly-diffused alloyed steel powder and prealloyed
steel powder (in which alloyed elements are already contained
when melted) are exemplified, and furthermore, hybrid steel
powder is exemplified, in which alloyed elements are partly
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diffused in the prealloyed steel powder.
The content of impurities in the iron-based powder may
be about 3 mass% or less in total. The content of each of
typical impurities is as follows: C is 0.05 mass% or less, Si
is 0.10 mass% or less, Mn (in the case that Mn is not added
as an alloy element) is 0.50 mass% or less, P is 0.03 mass%
or less, S is 0.03 mass% or less, 0 is 0.30 mass% or less, and
N is 0.1 mass% or less.
For the alloyed steel powder, Cr, Mn, Ni, Mo, V, Ti, Cu,
Nb and the like can be alloyed. In particular, Ti, Ni, Mo,
Cu and the like can be added even by diffusion bonding. If
the precondition as the iron-based powder (Fe content is 50
mass% or more) is satisfied, other alloy elements are not
particularly limited in content.
.T.verage particle diameter of the iron-based powder is
preferably adjusted to be in a typically used range for powder
metallurgy, that is, in a range of about 70 to 100 m. The
particle diameter of the Powder is shown as a measurement value
by a sieving method according to JIS I 2510, unless otherwise
specified.
Hereinafter, a specific composition of alloyed steel
powder particularly preferable for a material of a
high-strength sintered body is exemplified.
(Iron-based powder example 1)
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As a first example, prealloyed steel powder is preferably
shown, which contains Mo of 0.3 to 0.5 mass%, Mn of 0.1 to 0.25
mass%, and the remainder being Fe and inevitable impurities.
In the light of productivity, the steel powder is preferably
water-atomized alloyed steel powder, which is manufactured by
water-atomizing the steel having the above composition.
The reason for a preferable range of each component is
as follows.
= Mo: 0.3 to 0.5 mass%
Mo is an element that increases strength of a sintered
part by solution hardening or improvement in hardenability
(quench hardenability) of alloyed steel powder. When Mo
content is less than 0. 3 mass%, an effect of increasing strength
of the sintered part by Mo is not obtained. On the other hand,
when the content is more than 0.5 mass%, since the effect of
increasing strength of the sintered Part is saturated,
machining performance is unnecessarily reduced. Therefore,
Mo content is preferably adjusted to be in a range of 0.3 to
0.5 mass-%.
= Mn: 0.1 to 0.25 mass%
Mn is an element that increases strength of a sintered
part by solution hardening or improvement in hardenability of
water-atomized alloyed steel powder. When Mn content is less
than 0 .1 mass%, an effect of increasing strength of the sintered
part by Mn is not obtained. On the other hand, when the content
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is more than 0.25 mass%, oxidation of Mn easily proceeds,
leading to reduction in strength and compressibility of alloyed
steel powder. Therefore, Mn content is preferably adjusted
to be in a range of 0.1 to 0.25 mass%.
The rest of the powder other than the above components
preferably is Fe and inevitable impurities. The inevitable
impurities inevitably gets into the steel in a stage that an
ingot being a material of the water-atomized alloyed steel
powder is produced, or in a stage that water-atomized alloyed
steel powder is manufactured from the ingot.
A preferable method of manufacturing the water-atomized
alloyed steel powder is described, the method beino preferably
used in the invention. An ingot containing a predetermined
composition (that is, the above composition) is produced, and
then the ingot is formed into powder by a water atomizing method.
Furthermore, the obtained powder is subjected to finish
reduction and crushing (or pulverizing) thereby obtaining
water-atomized alloyed steel powder. An apparatus for
obtaining powder from an ingot by the water atomizing method
is not limited to a particular type, and any previously known
apparatus may be used as the apparatus.
<Alloying powder>
As the alloying powder, graphite powder, metal powder
of such as Cu, No and Ni, boron powder, cuprous oxide powder
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and the like are exemplified. Such alloying powder is mixed
to the iron-based powder, so that strength of a sintered body
can be increased.
The blending amount of the alloying powder is preferably
adjusted to be about 0.1 to 10 mass% in the iron-based powder
mixture. The reason for this is that the alloying powder is
blended by 0.1 mass% or more, so that strength of an obtained
sintered body is advantageously improved, on the other hand,
when it is blended by more than 10 mass%, dimension accuracy
of the sintered body is reduced.
In the case of the iron-based powder example 1,
particularly Cu powder of 1 to 3 mass% and graphite powder of
0.5 to 1.0 mass% are preferanly added.
C being amain component of graphite powder is an element
that increases strength of a sintered part by solution
hardening or improvement in hardenabilfty of water-atomized
alloyed steel powder. When the added amount of graphite powder
is less than 0.5 mass%, a desired effect is not sufficiently
obtained in the iron-based powder example 1. On the other hand,
when the content is more than 1.0 mass%, strength of the
sintered part is increased beyond necessity, and consequently
machining performance is unnecessarily reduced. Therefore,
the content of graphite powder is adjusted to be in a range
of 0.5 to 1.0 mass%.
Cu is an element that increases strength of a sintered
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part by solution hardening or improvement in hardenability of
alloyed steel powder. Moreover, Cu powder is melted during
sintering and thus changed into a liquid phase, causing
adhesion of particles of the alloyed steel powder to one another.
When the added amount of Cu powder is less than 1 rnass%, a desired
effect is not sufficiently obtained in the iron-based powder
example 1. On the other hand, when the amount is more than
3 mass%, since the effect of increasing strength of the sintered
part is saturated, machining performance is unnecessarily
reduced. Therefore, the content of Cu powder is adjusted to
be in a range of 1 to 3 mass% .
When Cu powder is added, if the added amount is within
the above range, an adding method may be a method where alloyed
steel powder is added with Cu powder and then simply mixed,
or a method of adhering Cu powder on a surface of water-atomized
alloyed steel powder via a binder. Moreover, it is acceptable
that the alloyed steel powder and the Cu powder are mixed and
subjected to heat treatment, so that the Cu powder is'
diffusion-bonded on a surface of the alloyed steel powder so
as to be formed into partly-diffused alloyed steel powder (or
hybrid alloyed steel powder) .
<Talc/steatite>
In the invention, it is important that at least one
selected from talc (3Mg0-4Si02) and steatite is blended.
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Steatite is sometimes called fired talc, and contains enstatite
(MgO-Si02) as a main component.
When talc or steatite is added together with fatty acid
amide, it exhibits a particularly large effect as a lubricant.
Moreover, while talc or steatite is one of MgO-Si02 composite
oxides known as free machining additives, if talc or steatite
is further added together with metallic soap, it exhibits a
particularly large effect even as a free machining additive.
The talc or steatite is blended as the lubricant, thereby
' compressibility of a compacted body is improved, in addition,
ejection force in compaction process is reduced, so that
compaction performance is remarkably improved. The reason for
this is considered as follows.
That is, it is considered that when talc and
steatite, are subjected to shear stress between iron-based
powder particles during compaction, each of the substances
tends to be cleaved along a crystal face, therefore frictional
resistance between particles within a compacted body is reduced,
and thus the particles easily move with respect to each other,
as a result, density of the compacted body is, improved. Such
an effect is effective in a region of a relatively low
compressive stress. On the other hand, in a high pressure
region, fatty acid amide exhibits an effect that it thinly
enters into a space between the particles so as to reduce
frictional resistance. It is considered that since the.
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frictional resistance is reduced over all the compressive
regions in this way, a synergetic effect is exhibited for
increasing density of the compacted body.
Moreover, it is considered that when talc or steatite
exists between a compacted body and a die, since the talc or
'steatite is cleaved due to shear stress applied from a die
surface during ejecting the compacted body, slidability of the
compacted body on the die surface is improved, leading to
reduction in ejection force.
Since the effects are exhibited regardless of
temperature of an iron-based powder mixture, the iron-based
powder mixture is not necessarily heated, and the effects
effectively contribute to increasing density of an iron-based
compacted body in compaction even at normal temperature.
Moreover, when the iron-based powder is heated, since plastic
deformation resistance of the iron-based powder is decreased
during compaction, higher density of a compacted body can be
obtained. Therefore, while heating temperature of the
iron-based powder can be appropriately set depending on a
required density of a compacted body, sufficient heating
temperature is less than 10000. More preferably, the heating
temperature is 8000 or less.
While the reason why machining performance is remarkably
improved is not elucidated, it is possibly considered that a
metal component in metallic soap reacts with talc/steatite
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during sintering, so that the metal component acts as an
auxiliary free machining additive. A sintered part
manufactured by using the powder mixture for powder metallurgy
of the invention may have high strength similar to that of a
usual high-strength sintered part, and in addition, may have
extremely excellent machining performance.
The blending amount of the talc or steatite is preferably
adjusted to be about 0.01 to 0.5 mass% in total in the iron-based
powder mixture. The reason for this is that such a lubricant
blended by 0.01 mass% or more, thereby density of a compacted
body can be adequately increased during compaction, and
ejection force can be adequately decreased during ejecting the
compacted body. Moreover, when an effect of improving
machining Derf o rma n c e is intended to be obtained, the lubricant
is preferably added by 0.01 mass% or more, too. When alloyed
steel powder for a high-strength sin:_ered body (for example,
the iron-based powder example 1) is used, to secure a stronger
effect of improving machining performance, the added amount
of talc and/or steatite is preferably adjusted to be 0.05 mass%
or more in total.
On the other hand, when the blending amount is more than
0.5 mass% or more, compressibility of the powder mixture is
reduced, which may reduce mechanical strength and the like of
a sintered body obtained by sintering the compacted body. More
preferably, an upper limit of the blending amount is 0.3 mass%,
CA 02642254 2008-08-12
=
and the upper limit is preferably adjusted to be 0.2 mass% or
less to substantially eliminate influence on mechanical
properties of the sintered body.
Prefeliy, talc has a monoclinic or triclinic crystal
structure, and steatite has a monoclinic crystal structure.
Size of talc or steatite is preferably about 1 to
pm in particle diameter.
<Fatty acid amide>
In the invention, at least one of fatty acid amides is
blended as a lubricant. Here, as the fatty acid amide, at least
one selected from fatty acid monoamide (such as stearic acid
monoamide ) and fatty acid bisamide (such as
ethylene-bis-stearoamide and methylene-bis-stearoamide) is
preferably used.
Each of them acts as not only a lubricant, but also a
binder. Therefore, by using each of them, segregation or
dusting of the relevant iron-based powder mixture is-
effectively prevented, and flowability and compaction
performance can be further improved. While a fatty acid is
sometimes mixed in fatty acid amide, this is not particularly
prohibited.
The blending amount of the fatty acid amide is preferably
adjusted to be about 0.01 to 0.5 mass% in the iron-based powder
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mixture. The reason for this is that when the blending amount
is less than 0.01 mass%, the adding effect is poor, and on the
other hand, when the blending amount is more than 0.5 mass%,
strength of a compacted body (or green compact) is decreased.
A lower limit of the blending amount is more preferably 0.03
mass% in the case that the iron-based powder is pure iron powder,
and 0.05 mass% in the case that it is alloyed steel powder.
An upper limit of the blending amount is more preferably 0.4
mass , and in the case that the iron-based powder is pure iron
powder, 0.3 mass% is furthermore preferable as the upper limit.
<Metallic soap>
In the invention, metallic soap can be further blended.
According to a previous common idea, the metallic soap is also
counted as a lubricant.
As the metallic soap, zinc stearate, lithium stearate,
calcium stearate and the like are listed. Among them, the zinc
stearate and the lithium stearate are particularly preferable.
The blending amount of the metallic soap is preferably
adjusted to be about 0.01 to 0.5 mass in the iron-based powder
mixture. The reason for this is that when the blending amount
is less than 0.01 mass , the adding effect is poor, and on the
other hand, when the blending amount is more than 0.5 mass ,
strength of a compacted body is. decreased. A lower limit of
the blending amount is more preferably 0.05 mass% or more, and
22
CA 02642254 2008-08-12
an upper limit thereof is more preferably 0.3 mass%.
The added amount of the fatty acid amide and the metallic
soap in total is preferably adjusted to be 0.1 mass% to 1.0
mass%. The lower limit is more preferably 0.2 mass%, and the
upper limit is more preferably 0.6 mass%.
Furthermore, the blending amount of the talc/steatite,
the fatty acid amide, and the metallic soap in total is
preferably adjusted to be about 0.01 to 2.0 mass% in the
iron-based powder mixture. The lower limit is more preferably
0.15 mass%, and the upper limit is more preferably 0.8 mass%.
<Other materials>
While other additives are not particularly needed for
the iron-based powder mixture of the invention, a known
additive such as surface modification agent (including
siloxanes) may be further added by about 0.5 mass% or less.
<Method of manufacturing powder mixture>
Next, a method of manufacturing the iron-based powder
mixture of the invention is described.
(First method)
Iron-based powder is added with the respective materials
(such as talc, steatite, fatty acid amide, metallic soap, and
alloying powder) , arid then subjected to primary mixing. Then,
a mixture after primary mixing is agitated while it is heated
23
CA 02642254 2008-08-12
to a melting point or higher of at least one of the fatty acid
amide and metallic soap, and then the mixture is gradually
cooled while being mixed. As a result, the alloying powder
or other material powder is adhered on the iron-based powder
by an effect of the melted material.
That is, the material, which is melted and used for
adhesion, acts even as a binder.
(Second method)
As a method similar to the first method, it is also
possible that the iron-based powder is added with only some
of the materials, and subjected to primary mixing, and then
further added with the rest of the materials, and subjected
to secondary mixing. The material subjected to secondary
mixing exists in the powder mixture in a free state. As a
particularly preferable example, a method is given, in which
at least part of the metallic soap is supplied for the secondary
mixing, and the rest of the materials is supplied for the
primary mixing, and fatty acid amide, or a co-melt of the fatty
acid amide with the metallic soap is used for the binder.
According to the method, the added amount of each material to
be blended to the iron-based powder can be minimized.
Mixing means of the iron-based powder and each material
is not particularly limited, and any of previously known mixers
can be used. In particular, a high-speed mixer, counter
24
CA 02642254 2008-08-12
current mixer, plough share mixer, and conical mixer, in each
of which the material powders being easily heated, are
particularly advantageously suited.
<Method of manufacturing compacted body and sintered body>
Next, a method of manufacturing an iron-based compacted
body using the iron-based powder mixture of the invention, and
a method of manufacturing an iron-based sintered body (sintered
part) are described:
The iron-based powder mixture of the invention can be
made into a compacted body by a typical compaction method.
Specifically, the iron-based powder mixture is filled into a
die, and furthermore subjected to compaction. As a typically
preferable condition of compaction, pressing force is
preferably adjusted to be 400 to 1000 M:Pa. Moreover, the die
may be heated to 50 to 70 C. Alternatively, the powder mixture
for powder metallurgy and the die may be heated to 80 to 130 C.
The iron-based powder mixture of the invention can be
adequately compacted in high density even at normal temperature,
and preferably compacted at normal temperature in the light
of productivity. However, the iron-based powder mixture or
the die may be advantageously heated, and the die may be
advantageously coated with a lubricant.
When the powder mixture is compacted in a heated surround,
temperature of the iron-based powder mixture or temperature
CA 02642254 2008-08-12
of the die is preferably adjusted to be less than 100 C. The
reason for this is that since the iron-based powder mixture
according to the invention is high in compressibility, the
powder mixture exhibits excellent compaction performance even
at a temperature of less than 100 C, and when the temperature
is more than 100 C, there is fear that the powder mixture may
be degraded due to oxidation. More preferably, the
temperature is 80 C or less.
Next, the high density, iron-based compacted body
obtained in the above way is ejected from the die, then
subjected to sintering so as to be formed into a high-density
sintered body. A sintering method is not particularly limited,
and any of previously known sintering methods can be preferably
used. In the sintering, Preferably, heating temperature is
1100 to 1600 C, and heating time is 10 to 60 min.
Sintering is performed in this way, thereby a sintered
part having excellent strength and excellent machining
performance (particularly, a high-strength sintered part in
the case of using alloyed steel powder) is obtained.
After sintering, a sintered part can be subjected to heat
treatment such as carburizing and quenching (gas carburizing
heat treatment) , bright hardening, induction hardening, and
carbonitriding heat treatment, so that strength of the (high
strength) sintered part can be further increased. Furthermore,
tempering may be performed.
26
CA 02642254 2008-08-12
[Examples]
Hereinafter, the invention is specifically described
according to examples.
Table 1 shows various types of iron powder for powder
metallurgy (each having an average particle diameter of about
80 rim) used as the iron-based powder in examples 1 to 4.
Particularly, in the case of alloyed steel powder, whether the
alloyed steel powder is ID rea2_loyed steel powder, partly alloyed
steel powder, or hybrid steel powder in which the prealloyed
steel powder is partly diffused with an alloyed element is
distinctively shown.
Table 1
Symbol Type of iron-based powder Category of alloyed steel powder
A Atomized pure iron powder
Reduced pure iron powder
o Fe-2%Cu Partly alloyed steel powder
Fe-4%Ni-1.5%Cu-0'.5%Mo Partly alloyed steel powder
Fe-2%Ni-1%Mo Partly alloyed steel powder
Fe-0,5%Ni-0.5 /0Mo Prealloyed steel powder
Fe-0.6 /0Mo Prealloyed steel powder
(Fe-0 .5%114o)-[0.2%Mol Hybrid steel powder*
Fe-0.45%Mo Prealloyed steel powder
(Fe-0.45%Mo)-[0.15%Mo Hybrid steel powder*
(Fe-1.5%Mo)-{2 //ciNi] Hybrid steel powder*
* inside of parenthesis: composition of prealloyed steel powder
inside of bracket: composition being diffusion-bonded to
the prealloyed steel powder
27
CA 02642254 2008-08-12
(Example 1)
Various types of iron-based powder as shown in Table 2,
and natural graphite powder (average particle diameter of 5
m) and/or copper powder (average particle diameter of 25 m)
were added with various types of lubricant powder (primary
additives), then heated to 140 C while being mixed by a
high-speed mixer, and then cooled to 60 C or lower, and further
added with various types of lubricant powder (secondary
additives), and agitated for 1 min at 500 rpm. Then, a powder
mixture was discharged from the mixer. A type and blending
amount of each of the primary and secondary additives are
collectively shown in Table 2. The added amount (part by mass)
of a lubricant is expressed in percentage of total mass of 100%
of the iron-base powder, natural graphite powder, and copper
powder. While the percentage is expressed using a numerical
value being not included in that of the total mass, the
percentage is approximately the same as in the case that it
is expressed using a numerical value being included in that
of the total mass . Average particle diameter of the talc powder
and average particle diameter of the steatite powder were 6 m
and 4 m respectively.
For comparison, powder mixtures were prepared (refer to
Table 3) in a way that various types of powder having the same
components as the above, each including the iron-based powder,
and natural graphite powder and/or copper powder, were added
28
CA 02642254 2008-08-12
with zinc stearate of 0.8 mass%, then the powder was mixed by
a V-container-turning mixer. Each of
the comparative
materials has a composition typically used in normal
compaction.
Next, each of the obtained iron-based powder mixtures
was filled in a superhard tablet-shaped die having an inner
diameter of 11 mm, and compacted at 490 MPa and 686 MPa. In
such compaction, when a compacted body was ejected from the
die, ejection force was measured, and green density of each
of obtained compacted bodies was measured.
Separately from this, the obtained iron-based powder
mixtures were subjected to compaction for preparing test pieces
for a machining test (outer diameter of 60 mm, inner diameter
of 20 mm, and length of 30 mm). In the compaction, pressing
force was 590 MPa. Sintering was performed in an RX gas
atmosphere, wherein heating temperature was 1130 C, and
heating time was 20 min. In
evaluation of machining
performance, while a cermet cutting tool was used, a machining
test was performed with cutting speed of 200 m/min, feed of
0.1 mm per unit, depth of cut of 0.3 mm, and a cutting distance
of 1000m, and flank wear width of the cutting tool was measured.
Smaller flank wear width of the cutting tool shows more
excellent machining performance of a sintered body.
Obtained results are shown in Table 4.
29
CA 02642254 2008-08-12
Table 2
Iron-based powder Natural ' Copper powder Primary
additive Secondary additive
__________________ graphite lubricant* lubricant*
type ' Blending powder VIDe Blending type Blending type
Blending
amount (mass%) amount amount amount
. (mass%) I (mass%) (mass%) (mass%)
Inventive C 99.4 0.6 1 - 0 STAM 0.1 Steatite
0.1
example 1 EBS 0.1 STZN 0.02
- EBS , 0.08
,
, I , _ , +-
_ , STLI 1 0.1
Inventive A ' 97.2 0.8 Electrolytic 2.0 STAM , 0,1
STZN 1 0.1
example 2 copper EBS I 0.1 EBS ' 0.02
. powder Steatite 0,1 STLI 0.08
I
Inventive A . 97.9 0.6 Atomizea 1.5 SIAM 0.1
STZN 0.02
example 3 i copper EBS 0.1 EBS 0.08
powder Steatite 0.1 STLI 0.1
Inventive B , 97.2 0.8 ' Electrolytic ' 2.0 SIAM 0.1
Steatite 0.1
example 4 copper EBS ' 0.1 STZN 0.02
' powder - EBS 0.08
- - STLI 0,1
inventive ID 99,7 0.3 - 0 SIAM 0 1 STZN
0.02
example 5 EBS 0.1 EBS 0.08
Steatite 0.1' = STLI 0,1
Inventive F 99,5 0.5 0 SIAM 0.1 Steatite 0,1
example 6 EBS 0.1 STZN 0.02
- - EBS 0.08
- - STLI 0.1
inventive G 97.5 0.5 Electrolytic 2.0 SIAM 0.1
Talc 0.1
example 7 copper EBS 0.1 STZN 0.02
powder EBS 0.08 I
- - STL1 0.1
1
inventive H 99.5 0.5 0 SIAM 0.1 'laic
0.1
example 8 EBS 0.1 STZN 0.02
- - EBS 0.08
- ISTLI 0.1
Inventive I 97.2 0.8 Atomized 2,0 1 SIAM I 0.1
Steatite 1 0.1
example 9 copper EBS 0.1 SIAM 0.04
powder - - EBS 0.04
STZN 0.02
. 1 - - , STLI 0.1
,
,
* EBS: ethylene -bis -stearoamide, STZN: zinc stearate, STAN:
stearic acid mcncamide, STLI: lithium stearate
CA 02642254 2008-08-12
Table 3
1 Iron-based powder Natural graphite j Copper powder
Added
type Blending amount powder (mass%) type
Blending amount lubricant*
(mass%) (mass%)
'
Comparative C 99.4 0,6 - 0
0.8 mass%
example 1 1
STZN
Comparative A 97.2 ' 0.8 Electrolytic copper 2.0
0.8 mass%
example 2 powder
STZN
Comparative A 97.9 0.6 I Atomized copper
1.5 0.8 mass%
example 3 powder .
STZN
Comparative B 97.2 I 0.8, Electrolytic copper 2.0
0.8 mass%
1 example 4 powder
STZN
Comparative D 99.7 '1 0.3
I 0
0.8 mass%
example 5 1
STZN
Comparative F 99.5 0.5 - . 0
0.8 mass%
example 6
STZN
Comparative G 97.5 0.5 Electrolytic copper . 2.0
0.8 mass% .
example 7 powder
STZN
Comparative H 99.5 0,5 = . . - 0
0.8 mass%
i
example 8 I
STZN
,
Comparative I 97.2 . , ,- - 0.8. , - -.
Atomized' copper 2.0 = 0.8 mass%
I example 9 " " I powder =-
. : , STZN
* STZN:, zinc stearate
Table 4
Iron-based Green density (Mg/m3) Ejection torce
(MPa) Cutting tool
powder .
1 Type 490 MPa 686 MPa 490 MPa i
686 MPa Flank wear
I compaction compaction compaction
I compaction width (mm)
Inventive example 1 C 6.99 7.25 1318
0.15
1 I 1
Inventive example 1 A J 7.01 7.26 13 18
0.20
2
Inventive example i A 7.00 7.26 .13 17
0.18
3
= inventive example B 6.86 7.09 11
20 0.21
4
Inventive example 0 I 7.00 .7.25 13 17
0.48
Inventive example F 6.91 7.19 14 18
0.15
6
Inventive example G 6.96 7.21 12 18
0.05
7
inventive example H ' .6.98 j 722 I 11 18
0.12
8
Inventive example i 6.98 7.22 12 20 -
0.03
9 -
Comparative C 6,96 7.11 11 . 19
0.35
example 1
Comparative A 6.97 1 7.12 12 18
0.55
example 2
Comparative A 6.97 7.12 12 17
0,48
example 3
Comparative B 1 6.81 6.99 10 18
0.58
example 4
Comparative D 6.94 7.15 13 I 18
0.98
' example 5
Comparative F 6.84 7.09 14' 19
0.43
example 6
Comparative G 6.85 7.08 13 19
0.22
example 7
Comparative H 6.85 7.09 I 12 19
0.31
example 8
Comparative I 6.85 7.09 1 13 20
0.11
example 9 I
31
CA 02642254 2008-08-12
As clear from a comparison between the inventive examples
1 to 9 and the comparative examples 1 to 9 as shown in Tables
2 to 4, the lubricants according to the invention are used as
lubricants, thereby a high-density compacted body can be
obtained without significantly increasing ejection force even
in the case of normal temperature compaction, and furthermore,
machining performance is remarkably improved.
(Example 2)
Various types of iron-based powder as shown in Table 5,
and natural graphite powder and/or copper powder were added
with various lubricants (primary additives), then heated to
140 C while being mixed by a high-speed mixer, and then cooled
to 60 C or lower, and further added with various lubricants
(secondary additives) , and agitated for 1 min at 500 rpm. Then,
a powder mixture was discharged from the mixer. A tvpe and
blending amount of each of the primary and secondary additives
are collectively shown in Table 5. Used materials are those
described in Table 1 as in the example 1.
For comparison, powder mixtures were prepared in a way
that various types of powder having the same components as the
above, each including the iron-based powder, and natural
graphite powder and/or copper powder, were added with
ethylene-bis-stearoarnide of 0.6 mass%, then the powder was
32
CA 02642254 2008-08-12
mixed by a V-container-turning mixer (comparative materials) .
Next, each of the obtained iron-based powder mixtures
was filled in a superhard tablet-shaped die having an inner
diameter of 11 mm, which was heated beforehand such that
temperature of a cavity wall surface was increased to 80 C,
and then the powder mixture was compacted at 490 MPa and 686
MPa. In such compaction, when a compacted body was ejected
from the die, ejection force was measured, and green density
of each of the obtained compacted bodies was measured.
Moreover, each of the comparative materials was
compacted at a typical compaction condition of warm compaction,
that is, the comparative material was heated to 120 C, then
filled into a superhard tablet-shaped die having an inner
diameter of 11 mm and which was heated to 130 C, and then
compacted at 490 MPa and 686 MPa. In such compaction, when
a compacted body was ejected from the die, ejection force was
measured, and green density of each of the obtained compacted
bodies was measured.
Moreover, test pieces for a machining test were prepared
by compaction as in the example 1, so that machining performance
was examined.
Obtained results are shown in Table 6.
33
CA 02642254 2008-08-12
Table 5
Iron-based powder Natural Copper powder Primary '
additive I Secondary additive
graphite lubricant* lubricant*
type Blending powder type Blending type Blending type Blending
amount (mass%) amount amount amount
(mass%) (mass%) (_mass%) (mass%)
Inventive A 97.2 0.8 Electrolytic 2.0 SIAM 0.1 Talc
0.1
example 10 copper EBS 0.1 STZN 0.02
powder- - I EBS 0.08
-
I ; STD 0.1
Inventive D 99.7 0.3 - 0 SIAM 0.1 STZN i 0.02
example 11 I EBS 0.1 ; EBS 0.08
I Steatite 0.1 I STL1
0.1
inventive H 99.35 G.6,5 . Q ,' 'N44 f 0.1 Talc ..
O.1
r'
_ ,
example 12 r ,7r-BS 0.1 I STZN -
-t.t
- - EBS 0.08
- STLI I
0.1
Inventive E 99.4 0.6 - 0 SIAM 0.05 Steatite ,
0.1
example 13 EBS 0.05 , STZN 0.02
- - EBS 0.08
1
- - STLI i
0.1
I
Inventive J 99.35 0.65 - 0 SIAM 0.1 I Steatite
0.1
example 14 EBS 0.1 SIAM 0.04
- - EBS I
0.04
= - - STZN 1 0.02
- - STU '
0.1
Inventive K 99.7 0.3 - 0 SIAM 0.05 Steatite 0.1
example 15 EBS 0.05 SIAM 0.04
- EBS I
0.04
- STZN i 0.02
_ STLI i 0.1
Comparative A 97.2 0.8 Electrolytic 2.0 0.6 mass% EBS
example 10 copper
powder
Comparative D 99.7 0.3 - 0 0.6 mass% EBS
example 11
Comparative H 99.35 0.65 - 0 0.6 mass% EBS
example 12
Comparative E 99.4 0.6 - 0 0.6 mass% EBS
example 13
Comparative J 99.35 0.65 - 0 0.6 mass% EBS
example 14
Comparative K 99.7 0.3 - 0 0.6 mass% EBS
example 15 ,
* EBS: ethylene -bis -stearoamide, STZN: zinc stearate, STAM:
stearic acid monoamide, STLI: lithium stearate '
34
CA 02642254 2008-08-12
Table 6
Iron-based Green density (Mg/m3) Ejection force (MPa)
powder
Type 490 MPa 686 MPa 490 MPa 686 MPa
compaction compaction compaction compaction
Inventive example 10 A 7.10 7.30 = 14 15
Inventive example 11 D 7.05 7.30 16 = 17
Inventive example 12 H 7.01 7.26 18 19
i Inventive example 13 E 1 7.04 7.29 15 18
Inventive example 14 J I 7.02 I 7.27 . 18 20
Inventive example 15 , K 6.99 7.24 18 21
Comparative example A 7.11 7.30 15 16 1
I
r Comparative example t ., 7.11 7.32 16 18
Comparative example H 7.03 7.27 17 20
12 _
Comparative example E 7.09 7.30 15 19
13
Comparative example 1 ,1 II 7.02 7.27 17 19
14
Comparative example K 1 6.98 i 7.2319 22
I
I i I
I 1
As clear from a comparison between the inventive examples
10 to 15 and the comparative examples 10 to 15 as shown in Tables
5 to 6, the primary and secondary additives of the invention
were added as lubricants, thereby the die was simply heated
to a relatively low temperature of less than 1003C, so that
even if the powder mixture was not heated, a compacted body
having high density, which was similar to that of a typical
warm compacted body, was able to be obtained without causing
increase in ejection force.
Flank wear width (ram) of each inventive example was
reduced to about 20 to 40% of that of a comparative example
in the same grouping (number) , showing remarkable improvement
even in machining performance.
CA 02642254 2008-08-12
(Example 3)
Various types of iron-based powder as shown in Table 7,
and natural graphite powder and/or copper powder were added
with various lubricants (primary additives) , then heated to
140 C while being mixed by a high-speed mixer, and then cooled
to 60 C or lower, and further added with various lubricants
(secondary additives) , and agitated for 1 min at 500 rpm. Then,
a powder mixture was discharged from the mixer. A type and
blending amount of each of the primary and secondary additives
are collectively shown in Table 7. Used materials are the same
as in the example 1.
For comparison, powder mixtures were prepared in a way
that each of various types of powder was added with
ethylene-bis-stea-roamide having a respective weight, then
mixed by a V-container-turning mixer.
Next, each of the obtained iron-based powder mixtures
was heated to 60 C, then filled in a superhard tablet-shaped
die having an inner diameter of 11 mm, which was heated
beforehand such that temperature of a cavity wall surface was
increased to 80 C, and furthermore coated with lithium stearate
powder on its wall surface, and then the powder mixture was
compacted at 490 MPa and 686 MPa. In such compaction, when
a compacted body was ejected from the die, ejection force was
measured, and green density of each of the obtained compacted
bodies was measured.
36
CA 02642254 2008-08-12
Moreover, each of the comparative materials was
compacted at a typical compaction condition of warm compaction,
that is, the comparative material was heated to 12000, then
filled into a superhard tablet-shaped die having an inner
diameter of 11 mm and which was heated to 13000, and then
compacted at 490 MPa and 686 MPa. In such compaction, when
a compacted body was ejected from the die, ejection force was
measured, and green density of each of the obtained compacted
bodies was measured.
Moreover, test pieces for a machining test were prepared
by compaction as in the example 1, so that machining performance
was examined.
Obtained results are shown in Table 8.
Table 7
Iron-based powder Natural Copper powder Primary additive
Secondary additive
___________________ graphite lubricant* lubhcant*
type Blending powder type Blending type Blending type Blending
amount (mass%) amount amount amount
(mass%) (mass% I (mass%) (mass%)
Inventive A 97.2 0.8 Electrolytic 2.0 I STAM 0.2
Steatite 0.2
example 16 copper EBS 0.2 STZN 0.04
powder EBS C.16
Inventive G 99.35 0.65 0 1 SIAM 0.1 Talc
0.1
example 17 I EBS 0.1 STZN 0.02
, EBS 0,08
¨ STLI 0.1
Comparative A 97.2 0.8 Electrolytic 2.0 0.8 mass% EBS
example 16 copper
powder
Comparative G 99.35 0.65 0 0.6 mass% EBS
example 17
* EBS: ethylene-bis-stearoamide, STZN: zinc stearate, STAM:
stearic acid monoamide, SILT: lithium stearate
37
CA 02642254 2008-08-12
Table 8
Iron-based Compaction Green density (Mg/m3) Ejection force
(MPa)
powder temperature
Type Powder Die 490 MPa 686 MPa 490 MPa 686 MPa
( C) ( C) compaction compaction compaction
compaction
Inventive example A - 60 80 6.90 7.19 8 11
16
Inventive example G 60 ao 7,04 7.29 ' 15 19
17
Comparative A 120 130 6.94 7.2 1 9 12
1
example 16
' Comparative G 120 130 7.00 I 7.26 16 19
example 17
As clear from a comparison between the inventive example
16 and the comparative example 16, and a comparison betWeen
the inventive example 17 and the comparative example 17 as shown
in Tables 7 to 6, the primary and secondary additives of the
invention were added as lubricants, thereby the die and the
powder were simply heated to a relatively low temperature of
less than 100 C, so that a compacted body having high density,
which was similar to that of a typical warm compacted body,
was able to be obtained with an extremely low ejection force.
Flank wear width (mm) of each inventive example was
reduced to about 25 to 35% of that of a comparative example
in the same grouping (number), showing remarkable improvement
even in machining performance.
(Example 4)
Various types of iron-based powder as shown in Table 9,
and natural graphite powder and/or copper powder were added
with various lubricants (primary additives), then heated to
38
CA 02642254 2008-08-12
140 C while being mixed by a high-speed mixer, and then cooled
to 60 C or lower, and further added with various lubricants
(secondary additives) , and agitated for 1 min at 500 rpm. Then,
a powder mixture was discharged from the mixer. A type and
blending amount of each of the primary and secondary additives
are collectively shown in Table 9. Used materials are the same
as in the example 1. A comparative example 20 was subjected
to processing where the relevant powder was added with steatite
powder in place of the primary and secondary additives, then
mixed by the high-speed mixer at the same condition as in the
. above.
Next, each of the obtained iron-based powder mixtures
was filled in a superhard tablet-shaped die having an inner
diameter of 11 mm, and compacted at 490 MPa and 686 MPa. In
such compaction, when a compacted body was ejected from the
die, ejection force was measured, and green density of each
of obtained compacted bodies was measured.
Separately from this, the obtained iron-based powder
mixtures were subjected to compaction for preparing tensile
test pieces according to Japan Powder Metalluray Association
JPMA M04-1992, and test pieces for a machining test (outer
diameter of 60 mm, inner diameter of 20 mm, and length of
30 mm). In the compaction, pressing force was 590 MPa.
Sintering was performed in an RX gas atmosphere, wherein
heating temperature was 1130 C, and heating time was 20 min.
39
CA 02642254 2008-08-12
An evaluation method of machining performance was the same
as in the example 1.
Obtained results are shown in Table 10.
Table 9
Iron-based powder Natural Copper powder Primary additive
Secondary additive 1
___________________ graphite lubricant lubricant*
type Blending powder type Blending type Blending type Blending
amount (mass%) amount amount amount
(mass%) (mass%) j (mass%) (mass%)
Comparative D 99.4 0.6 - 0 STAM 0.1 STLI 0.1
example 18 EBS 0.1 STZN 10.02
- - EBS 0.08
'
Inventive D 99.4 0.6 - 0 STAM 0.1 Steatite 0.05
example 18 I EBS 0.1 STLI 10.1
- STZN 0.02
- EBS 0.08
Inventive I D 99.4 1 0.6 0 STAM 0.1 Steatite
0.1
example 19 I EBS 0.1 STLI L 0.1
- STZN 0.02
- EBS 0.08
Inventive D 99.4 0.6 - 0 STAM 0.1 Steatite 0.2
example 20 EBS 0.1 STLI 0.1
- ISTZN 0.02
EBS 0.08
inventive D I 99.4 1 0.6 0 SIAM I 0.1 Steatite
0.3
example 21 1 EBS 0.1 STLI 0.1
-I - 1 STZN I
0.02
- H EBS 0.08
Comparative D 99.4 0.6 0 1 SIAM 0.1 Steatite
0.6
example 19 EBS 0.1 STLI 0.1
- -1 STZN 1 0.02
- - EBS 0.08
Inventive I 97.2 0.8 Electrolytic 2.0 STAM i 0.1
I Steatite 0.1
example 22 copper EBS 0.1 STLI 0.1
powder STZN 0.1 - -
Comparative I 97.2 0.8 Electrolytic 2.0 Steatite 0.1 -
example 20 copper
powder
Inventive I 97.2 0.8 Electrolytic 2.0 SIAM 0.2
Steatite 0.1
example 23 copper EBS 0.2 - -
. powder
Comparative 1 97.2 0.8 l Electrolytic 2,0 STZN 1 0.2
1 Steatite 0.1
example 21 I copper STLI I
0.2
powder
* EBS: ethylene -bis -stearoamide, STZN: zinc stearate, STAN:
stearic acid monoamide, STLI: lithium stearate
= CA 02642254 2008-08-12
Table 10
Iron-based Green density (Mg/m3) Ejection
force (MPa) Sintered Cutting tool
powder body
Type 490 MPa 686 MPa 490 MPa 686
MPa Tensile Flank wear
compaction compaction compaction
compaction strength width (mm)
(MPa)
. Comparative D 6,99 7.24 14 18
630 0.92
example 18
Inventive I D 6.99 7.25 13 17 625
0.65 .
example 18
Inventive D , ' 7.00 7.25 12 16 ' 610
0.54
example 19 , ,
Inventive D ' 6.97 ' 7.23 13 17 590
0.51
example 20 11
Inventive D 6.95 7.21 = 13 18
550 ' 0.45
example 21 ,
Comparative D ' 6.94 I 7.20 15 19 490
0.43
example 19
Inventive - I 6.99 ' 7.23. 12 18 620 '
0.03
example 22
I Comparative I Compaction is disabled due to galling.
1
I example 20
i
Inventive I 6.98 I 7.22 13 I 19 630 1
0.05
example 23 ! I 1
1 Comparative I 6.96 1 7.20 20 j 20 ' 610 1
0.06
1 example 21 . 1. I
I
As clear from a comparison between the inventive examples
18 to 21 and the comparative examples 18 and 19 as shown in
Tables 9 to 10, in the iron-based powder mixture in which
steatite and the like are added within a range of the invention,
a high-density compacted body can be obtained without
increasing ejection force. In the comparative example 19 in
which steatite and the like are added in a range of more than
0.5 mass%, mechanical Properties are significantly reduced.
Furthermore, it is known from the inventive examples 18 to 21
that the added amount of steatite and the like is more
preferably 0.2 mass% or less in the light of the mechanical
properties.
As clear from a comparison between the inventive examples
22 and 23 and the comparative examples 20 and 21, fatty acid
41
CA 02642254 2008-08-12
amide and the like need to be added with steatite and the like
to obtain a high-density compacted body without increasing
ejection force. Moreover, it is known that metallic soap is
further added, thereby machining performance of a sintered body
can be remarkably improved.
(Example 5)
Water-atomized alloyed steel powder having a composition
shown in Table 11 was manufactured by a water-atomizing method.
The rest of the powder other than Mn and Mo is Fe and inevitable
impurities. The water-atomized alloyed steel powder was added
with Cu powder, graphite powder, talc, and steatite in a ratio
as shown in the Table 11. Each of Mo. content and Mn content
(mass%) in the water-atomized:steel powder, or each of the added
amount (mass%) of the Cu powder, graphite powder, talc, and
steatite to be added to the water-atomized steel powder is shown
in percentage of mass of a powder mixture for powder metallurgy,
the percentage being expressed usind a numerical value included
in a numerical value of mass of the powder mixture.
Furthermore, a lubricant was added in a ratio as shown
in Table 11. The added amount (part by mass) of the lubricant
is shown in percentage of mass (100 part by mass) of a powder
mixture for powder metallurgy obtained by mixing the
water-atomized alloyed steel powder and additives, the
percentage being expressed using a numerical value being not
42
CA 02642254 2008-08-12
included in a numerical value of moss of the powder mixture
(but, the percentage is approximately the same as in the case
that it is expressed using a numerical value included therein) .
Next, the materials were mixed by a V blender, then an
obtained powder mixture for powder metallurgy was filled in
a die so as to be subjected to compaction for preparing tensile
test pieces according to Japan Powder Metallurgy Association
JPMA M04-1992, and test pieces for a machining test (outer
diameter of 60 mm, inner diameter of 20 mm, and length of 30
mm) . In the compaction, pressing force was 590 MPa. Sintering
was performed in an RX gas atmosphere, wherein heating
temperature was 113000, and heating time-was 20 min.
Tensile strength obtained by a tensile test was as shown
in Ta3-1., 11.
In evaluation of machining performance, while a cermet
cutting tool was used, a machining test was performed with
cutting speed of 200 m/M.7.n, feed of 0.1 mm per unit, depth of
cut of 0.3 mm, and a cutting distance of 1000m, and flank wear
width of the cutting tool was measured. Results of the
measurement are as shown in Table 11. Smaller flank wear width
of the cutting tool shows more excellent machining performance
of a sintered body.
In Table 11, inventive examples use a powder mixture for
powder metallurgy that satisfies the scope of the invention,
and comparative examples use a powder mixture for powder
43
CA 02642254 2008-08-12
metallurgy that departs from the scope of the invention. In
a prior-art example of No. 22, a powder mixture for powder
metallurgy using Fe-4Ni-1.5Cu-0.5Mo water-atomized alloyed
steel powder, which is previously practically used, is blended
with a conventional lubricant. Numerical values added to
respective alloy elements of No. 22 are expressed in mass%.
44
,
CA 02642254 2008-08-12
Table 11
No Powder mixture for powder metallurgy (mass%)*1 Lubricant 1
Lubricant 2 Sintered Cutting Remarks
body tool
Water-atomized Cu Graphite Talc I Steatite Type I Added
Type Added Tensile Flank
alloyed steel powder powder *2 amount *2 amount strength wear
powder (part (part (MPa) width
Mo Mn by by (mm)
mass) mass)
; 1 1 0.45 0.21 I 0.0 j 0.8 ' 0.1 H- EBS 0.4 1 -
( -( 380 0.04 1 Inventive 1
i example
2 i 0.45 ' 0.21 1.5 0.8 0.1 - EBS ' 0.4 I -
r 520 0.08 Inventive
I example
3 0.45 0.21 2.0 ' 0.8 0.1 - EBS 0.4 - i
1 630 0.08 Inventive
example
4 0.45 0.21 3.0 0.8 0.1 ' - ' EBS 0.4 - - 650
0.15 Inventive
, example
6 0.45 0.05 2.0 0.8 - 0.1 STAM 0.2 STZN 0.2 480 0.02
Comparative
example
7 0.45 0.12 2,0 0.8 - 0.1 SIAM 0.2 STZN 0.2
550 , 0.02 . Inventive
example
8 0.45 0.19 2.0 0.8 - 0.1 SIAM 0.2 STZN 0.2 640 0.04
Inventive
example
0.2 0.20 2.0 0.8 0.1 0.1 STAM 0,4 - - 430 0,07
inventive
example
11 0,3 0.20 2.0 0.8 0.1 0.1 STAM 0,4 - 540 0.07
Inventive
example
12 0.5 0.20 2.0 0.8 0,1 0.1 STAM 0.4 - - 630 0.07
Inventive
example
14 0.45 0.21 2.0 0.4 0.1 - EBS 0.5 - - 410 0.05 Inventive
example
0.45 0.21 2.0 0.6 0.1 - EBS 0.5 - 530 0.05 Inventive
example
16 0.45 0.21 2.0 0.9 0.1 - EBS 0.5 - - 620 0.10 inventive
example
18 0.45 0.21 2.0 0.8 - I - EBS 0.3 I STLI 0.15
650 0.30 Comparative
example
19 0.45 10.21 2.0 0.8 - 0.3 EBS 0.3 STLI 0.15 640 0.02
Inventive
example
10.45 0.21 2.0 0.8 - 0.5 EBS 0.3 STLI 0.15
600 0.02 inventive
example
21 0.45 I 0.21 2.0 0.5 1 -I 0.7 1 EBS 0.2 STLI
1 0.15 460 ' 0.01 Comparative
! example
22 Fe-4N1-1.5Cu-0.5Mo 0.5 . - ' - BS 10.5 EBS ' 0.5
590 0.48 Prior-art
, example
*1 percentage of mass of powder mixture for powder metallurgy
(by a numerical value included in a numerical value of the mass)
*2 EBS: ethylene-bis-stearoamide, STZN: zinc stearate, STAM:
stearic acid monoamide, STLI: lithium stearate
*3 percentage of mass of powder mixture for powder metallurgy
(by a numerical value not included in a numerical value of the
mass)
CA 02642254 2008-08-12
As obvious from Table 11, particularly, any of sintered
bodies obtained from the powder mixtures for powder metallurgy
of the inventive examples are excellent in mechanical
properties and machining performance. The prior-art example
is particularly significantly bad in machining performance of
a sintered body.
When the water-atomized alloyed steel powder contains
Mo of 0.3 to 0.5 mass% and Mn of 0.1 to 0.25 mass%, and the
powder mixture contains Cu powder of 1 to 3 mass% and graphite
powder of 0.5 to 1.0 mass%, a sintered body can be obta.ined,
which has a tens', le strength of 500 Ma or more., and is excellent
in machining performance.
Industrial Applicability
According to the invention, an iron-based powder mixture
can be obtained, which gives high compaction density and small
ejection force even if the powder mixture is compacted at low
temperature of about room temperature. Moreover, according
to a preferred invention, a powder mixture for powder
metallurgy can be obtained, wit:ich is preferable for machining
a sintered .part having excellent machining performance,
particularly, preferable for machining a high-strength
sintered part.
Moreover, according to the invention, the iron-based
powder mixture is used as a material, thereby an iron-based
46
CA 02642254 2008-08-12
compacted body having high compaction density can be obtained,
and furthermore, an iron-based sintered body can be obtained,
which has high sintering density, or has further excellent
machining performance.
47
