U.S. patent application number 11/249875 was filed with the patent office on 2006-05-04 for liquid, its use for the preparation of powder mixtures on the basis of iron or stainless steel as well as a method for the preparation of powder mixtures on the basis of iron or stainless steel.
This patent application is currently assigned to Zschimmer & Schwarz GmbH & Co. KG Chemische Fabriken. Invention is credited to Michael Holzgen, Peter Quirmbach, Alfred Vuin.
Application Number | 20060090592 11/249875 |
Document ID | / |
Family ID | 35511673 |
Filed Date | 2006-05-04 |
United States Patent
Application |
20060090592 |
Kind Code |
A1 |
Quirmbach; Peter ; et
al. |
May 4, 2006 |
Liquid, its use for the preparation of powder mixtures on the basis
of iron or stainless steel as well as a method for the preparation
of powder mixtures on the basis of iron or stainless steel
Abstract
A liquid for the preparation of powder mixtures on the basis of
iron or stainless steel, comprising water, an inhibitor, and a
stabilizer, and a method of forming the same.
Inventors: |
Quirmbach; Peter;
(Hundsdorf, DE) ; Holzgen; Michael; (Ebernhahn,
DE) ; Vuin; Alfred; (Wiesbaden, DE) |
Correspondence
Address: |
KUSNER & JAFFE;HIGHLAND PLACE SUITE 310
6151 WILSON MILLS ROAD
HIGHLAND HEIGHTS
OH
44143
US
|
Assignee: |
Zschimmer & Schwarz GmbH &
Co. KG Chemische Fabriken
|
Family ID: |
35511673 |
Appl. No.: |
11/249875 |
Filed: |
October 13, 2005 |
Current U.S.
Class: |
75/231 |
Current CPC
Class: |
B22F 2998/10 20130101;
C22C 33/0207 20130101; B22F 2998/10 20130101; B22F 9/026 20130101;
C22C 33/0207 20130101; B22F 2009/043 20130101; B22F 2009/042
20130101; B22F 9/04 20130101; B22F 1/0059 20130101 |
Class at
Publication: |
075/231 |
International
Class: |
C22C 29/00 20060101
C22C029/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 4, 2004 |
DE |
10 2004 053 222.2 |
Claims
1. A liquid for the preparation of powder mixtures on the basis of
iron or stainless steel, containing a) water, b) inhibitor, c)
stabilizer and d) further materials as necessary.
2. The liquid according to claim 1, in which the inhibitor is at
least one of the following materials: benzoates, ethanolic boric
acid, phosphates and phophonates as well as benzotriazole,
tolytriazole, sodium mercapto benzotriazole, amino alkyl
benzimidazoles, molybdates, sodium nitrite, sebacates or
silicates.
3. The liquid according to claim 1, in which the inhibitor is at
least one of the following materials: carboxylic acids, amines or
their derivatives.
4. The liquid according to claim 1, in which the stabilizer is at
least one of the following materials: cellulose ether, alginate,
starch, starch ether, guar, guar ether or xanthane.
5. The liquid according to claim 1, in which at least one of the
further materials is a wax emulsion.
6. The liquid according to claim 5 with a wax emulsion on the basis
of at least one of the following materials: paraffin, oxidized
paraffin, polyethylene, polypropylene or amide wax such as for
example ethylene-bis-stearylamide, stearylamide or stearate.
7. The liquid according to claim 1, in which at least one of the
other materials is a dispersion agent.
8. The liquid according to claim 7, in which the dispersion agent
is a polyacrylic acid.
9. The liquid according to claim 1, in which at least one of the
other materials is a temporary binder.
10. A use of a liquid according to claim 1 for the preparation of
powder mixtures on the basis of iron or stainless steel.
11. The use of a liquid according to claim 10 as mixing liquid for
the preparation of powder mixtures on the basis of iron or
stainless steel.
12. A method for the preparation of powder mixtures on the basis of
iron or stainless steel, in which a powder mixture on the basis of
iron or stainless steel is initially mixed in a liquid in
accordance with claim 1 and is subsequently dried
13. The method according to claim 12 in which the drying is carried
out in a spray drying unit.
Description
[0001] The invention relates to a liquid, its use for the
preparation of powder mixtures of iron or stainless steel as well
as a method for preparation of powder mixtures on the basis of iron
or stainless steel.
[0002] In powder metallurgy, metal based powder mixtures in
particular on the basis of iron or stainless steel are used in
order to manufacture herefrom highly stress resistant parts.
[0003] For this purpose suitable iron or stainless steel powder
mixtures are at first prepared, pressed to form a molded part and
the molded part produced thereby (the green body) is then sintered
to the finished part.
[0004] Powder mixtures on the basis of iron or stainless steel are
generally compounded from an iron powder, an alloy powder, such as
for instance copper, graphite or iron phosphite powder as well as
another material, which is effective as an auxiliary pressing
aid.
[0005] For the auxiliary pressing aid, effective materials are
usually waxes or stearates, for example zinc, aluminum, lead or
especially ethylene-bis-stearate (EBS) are employed.
[0006] Powder mixtures of the type mentioned above tend to separate
out again. At the end of the preparation process for example of the
mixing step an optimal homogeneous powder mixture is generally not
present. The molded bodies manufactured from the correspondingly
inhomogeneous powder mixtures frequently have inadequate
properties.
[0007] It is moreover problematic that the powder mixtures which
are prepared as above, just lack green strength. The form shaping
and subsequent conservation of the shape of the green body is thus
very complicated. Finally the lacking green strength can lead to
the sintered molded body having inadequate properties.
[0008] Finally, the powder mixtures as prepared above tend to form
"dust" since the fines are not bonded sufficiently into the powder
mixture.
[0009] The basic object of the invention is to demonstrate a way of
preparing powder mixtures on the basis of iron and/or stainless
steel, while avoiding the disadvantages described above.
[0010] This object is solved in accordance with the invention by
providing a liquid for the preparation of powder mixtures on the
basis of iron or stainless steel which contains [0011] water [0012]
inhibitor [0013] stabilizer and [0014] further materials if
necessary
[0015] The basic recognition of the invention is that the
disadvantages in the preparation of powder mixtures on the basis of
iron and/or stainless steel described above can be prevented, if
the powder mixtures are not--as hitherto--prepared dry, but are
prepared in the liquid in accordance with the application, i.e.
especially are mixed herein.
[0016] For that the powder mixture on the basis of iron or
stainless steel is initially mixed in the liquid in accordance with
the application and subsequently dried.
[0017] The powder mixture can alone comprise an iron and/or
stainless steel powder as well as an alloy powder; the addition of
an auxiliary pressing aid such as a powdered stearate can be
dispensed with.
[0018] In order to prevent reaction of the water with the iron or
stainless steel powder, then especially for example to prevent its
hydrolysis the liquid has at least one inhibitor in addition to the
water.
[0019] Inhibitors have the object of coating the iron or stainless
steel based powder mixture or controlling the accumulation of
oxygen onto the particles of the powder mixture in such a way that
they do not hydrolyze in the water or undergo any other reaction
with the water.
[0020] Earlier investigations of mixing powder mixtures based on
iron in water regularly failed in that a reaction of the iron
particles with the water could not be prevented. By means of an
inhibitor, especially through one or a plurality of the inhibitors
named below, this reaction can henceforth be completely or at least
extensively forestalled.
[0021] As inhibitors, for example benzoates, ethanolamine boric
acid, phosphates and phosphonates as well as benzotriazole,
tolytriazole, sodium mercaptobenztriazole, aminoalkylbenzimidazol
and mixtures thereof can be used. Alternatively or cumulatively
molybdates, nitrites, sebacates, silicates and mixtures thereof can
be employed as inhibitor.
[0022] Up to now it was unknown that these substances are effective
as excellent inhibitors in the liquid preparation of powder
mixtures on the basis of iron or stainless steel or are effective
in the mixing of iron and stainless steel based powder mixtures in
water.
[0023] As other materials the liquid in accordance with the
application can contain auxiliary pressing aids.
[0024] As auxiliary pressing aids, wax emulsions can for example be
employed. The wax emulsion can for example be a wax emulsion on the
basis of paraffin, oxidized paraffin, polyethylene, polypropylene,
stearates, amide waxes such as for example
ethylene-bis-stearylamide, stearylamide or mixtures thereof.
[0025] It was recognized in accordance with the invention that wax
or a stearate is effective as a pressing aid and also in addition
as an inhibitor in a water-based liquid in which powder mixtures on
the basis of iron or stainless steel are mixed. The wax or stearate
can however only then be employed when it is present in the liquid
as an emulsion. The addition of wax or a stearate in non-emulsified
form would not lead to any distribution of wax in the water.
Correspondingly earlier tests failed to use water as liquid for the
preparation of iron-based powder mixtures since the non-emulsified
wax or stearate does not separate or distribute in the water.
[0026] The viscosity of the liquid is controlled by means of the
Stabilizer. In particular stabilizers in accordance with the
application are employed which increase the viscosity of the water
so that the settling of the components of the powder mixture in the
liquid is made difficult and demixing is thus opposed.
[0027] As stabilzers, for example celluloses can be employed, for
example celluloseether, for example hydroxyethylcelluloses,
hydroxypropylcelluloses, methylcelluloses,
methylethylhyroxycelluloses, methylpropylhydroxycelluloses or
mixtures thereof. Alternative or cumulatively alginates, starches,
starchethers, guar, guarether, xanthane or mixtures thereof can be
employed as stabilizers.
[0028] Cumulatively or alternatively to the inhibitors named above,
the liquid in accordance with the application can also contain as
inhibitor especially carboxylic acids and/or amines or their
particular derivatives. Especially carboxylic acid derivatives in
the amine neutralized state prove to be particularly effective
inhibitors.
[0029] As carboxylic acids, preferably dicarboxylic acids and/or
triazine derivatives are employed. Dicarboxylic acids can for
example be especially 1,8-octanedicarboxylic acid, 1,9-nonane
dicarboxylic acid, 1,10-decanedicarboxylic acid (sebacic acid),
1,11-undecanedicarboxylic acid, 1,12-dodecanecarboxylic acid and so
forth up to including 1,16-hexadecanedicarboxylic acid. Relative to
the triazine derivatives for example especially 1,3,5-triazine
derivatives, above all 1,3,5-triazine-2,4,6-triaminetricarboxylic
acid are provided.
[0030] As amines, preferably ethanolamine and/or imidazolines are
employed. Ethanolamines can for example in particular be
triethanolamine, diethanolamine, monoethanolamine and/or
trishydroxymethylaminomethane. Relative to the imidazolines, in
addition to polymers containing imidazole units also non-polymeric
imidazole derivatives, like for example
2-(2-heptadec-8-enyl-2-imidazoline-1-yl)ethanol are provided. Also
similar imdidazo compounds to the latter can be provided, for
example imidazoline derivatives, such as for example hydroxyethyl-,
aminoethyl- and/or amidoethyl-imdidazol derivatives. As alkyl
groups oleic and talloleic fatty acids up to octanoic acid can be
present.
[0031] It was determined in accordance with the invention that the
above named inhibitors are particularly effective when they are
present in combination with amines and carboxylic acids, in each
case especially of the previously stated type.
[0032] Surprisingly it was further determined, in accordance with
the invention that without exception the inhibitors named above,
especially also the previously mentioned carboxylic acids and
amines can control the viscosity of the liquid, they can thus
function as stabilizers. According to one embodiment it is
therefore provided to waive the addition of a separate stabilizer.
In this case the inhibitors used represent at the same time
stabilizers within the intent of the application.
[0033] At least one of the other materials in the liquid can for
example be a dispersion agent, for example polyacrylic acids.
[0034] A temporary binder can also be present in the liquid as
another material, for example a temporary binder on the basis of
polyacrylates, polyvinylacetates, polyvinylalcohols as well also as
cellulose and starch derivatives or mixtures thereof.
[0035] The preparation of powder mixtures on the basis of iron or
stainless steel are not only strongly improved through the use of
the liquid in accordance with the application, but also the
properties of the sintered molded parts produced from these
mixtures are markedly improved compared to the molded parts
according to the prior art.
[0036] So by use of the liquid in accordance with the application
powder mixture dust can be almost completely prevented.
[0037] Also the green strength of the formed green body can be
significantly increased.
[0038] The (sintered) molded parts manufactured from the powder
mixtures which have been prepared with the liquid in accordance
with the application exhibit excellent properties especially high
homogeneity and strength.
[0039] For the preparation of an iron and/or stainless steel based
powder mixture with the liquid in accordance with the application,
the powder mixture is initially mixed in the liquid in accordance
with the application and subsequently dried.
[0040] The homogenization of the powder mixture in the liquid in
accordance with the application can be carried out in known mixing
units, for example attritors.
[0041] The mixing duration in the liquid can amount to 1 to 3
hours.
[0042] After the mixing of the powder mixture in the liquid in
accordance with the application the moist powder mixture is taken
to a drying plant for example a spray drying installation.
[0043] In the drying plant, for example a spray drying
installation, the moist mixture is atomized to produce a
granulate.
[0044] Thereby a characteristic granulate forms from the mixed
powder mixture mixed in the liquid in accordance with the
application, which in addition to whole granular portions is also
characterized by hollow granulate.
[0045] On the basis of the regularly formed proportion of hollow
granulate the dried granulate can be very effectively formed by
means of forming tools, customarily in presses, into green
bodies.
[0046] Damage to the forming tool especially of the moving parts of
suchlike in the event of granulate dust is prevented by means of
the use of the liquid in accordance with the application.
[0047] As already indicated above, it was determined in accordance
with the invention that the wax emulsion in addition to its
property as a pressing aid, acts at the same time as an excellent
inhibitor, whereby the homogeneity and green density or strength of
the pressed molded part is increased at the same contact pressure
(in comparison to the contact pressure or the properties of a
molded part, that was prepared according to the prior art) or a
lower contact pressure is required in order to obtain the same
properties for the molded part, which was obtained without a wax
emulsion in the liquid in accordance with the application.
[0048] The green body is finally subjected to heat treatment and
thereby sintered to the iron or stainless steel product.
[0049] The liquid in accordance with the application can be
compounded for example as follows (the following data in wt % are,
unless stated otherwise, with respect to the total weight of the
liquid): [0050] water: 25-99 wt % thus for example thus 68-98 wt %
or 82-93 wt %; [0051] inhibitor: 0.02-50 wt %, thus for example
also 1-7 wt % or 1-4 wt %; [0052] stabilizer: 0.005-7 wt %, thus
for example also 0.05-4 or 0.1-1 wt %; [0053] other materials: 0-20
wt %.
[0054] Wax emulsion can for example be present in the liquid in
proportions from 0.5-35 wt % thus for example also in proportions
from 1-15 wt % or 4-12 wt %. Carboxylic acid can for example be
present in the liquid in proportions from 0.1-5 wt % thus for
example also in proportions from 0.5-4 wt %.
[0055] Amines can for example be present in the liquid in
proportions from 0.1-7 wt % thus for example also in proportions
from 0.5-5 wt %.
[0056] Dispersion agent can for example be present in the liquid in
proportions from 0.01-33 wt % thus for example also in proportions
from 0.05-6 wt % or from 0.1-3 wt %.
[0057] The liquid in accordance with the application can for
example be mixed with the moist mixture at 3 to 7 times the amount
of an iron or stainless steel based powder mixture.
[0058] In the following, three examples are given for a liquid in
accordance with the application:
EXAMPLE 1
[0059] water: 88.2 wt %; [0060] inhibitor in the form of
monoethanolamine borate: 2.2 wt %; [0061] stabilizer in the form of
methylcellulose: 0.4 wt %; [0062] wax emulsion in the form of a 50%
paraffin emulsion: 8.8 wt %; [0063] dispersion agent in the form of
polyammoniumacrylate: 0.4 wt %.
EXAMPLE 2
[0063] [0064] water: 84.7 wt %; [0065] inhibitor in the form of
monoethanolamine phosphate: 2.8 wt %; [0066] stabilizer in the form
of methylhydroxypropylcellulose: 0.6 wt %; [0067] wax emulsion in
the form of a 50% polypropylene emulsion: 11.3 wt %; [0068]
dispersion agent in the form of polyammoniumacrylate: 0.6 wt %.
EXAMPLE 3
[0068] [0069] water: 88.2 wt %; [0070] inhibitor in the form of
1,10-decanedicarboxylic acid: 2.1 wt %; [0071] inhibitor in the
form of triethanolamine: 2.1 wt % [0072] wax emulsion in the form
of a 50% paraffin emulsion: 7.6 wt %.
[0073] In example 3 the inhibitors at the same time perform the
function as stabilizer.
[0074] In the moist powder mixture of the liquid in accordance with
the application and the iron/stainless steel powder mixture,
besdides 100 wt % iron/stainless steel particles, for example the
following proportions of the liquid components can additionally be
present: [0075] 8-200 wt % water, thus for example also 12-70 or
12-30 wt % water; [0076] 0.05-10 wt % inhibitor, thus for example
also 0.2-2 wt % inhibitor; [0077] 0.01-5 wt % stabilizer, thus for
example also 0.05-1 or 0.05-0.5 wt % stabilizer.
[0078] Besides the 100 wt % iron/stainless steel particles and the
components previously mentioned for example 1-5 wt % wax emulsion,
thus for example also 0.1-20 or 0.5-4 wt % wax emulsion and/or
0.01-5 wt % dispersion agent thus for example also 0.05-1
dispersion agent can be present in the moist mixture.
* * * * *