Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02221778 1997-11-21
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SLEEVES, THEIR PREPARATION, AND USE
FIELD OF THE INVENTION
This invention relates to exothermic and/or insulating sleeves, their method
of
s preparation, and their use. The sleeves are prepared by shaping a sleeve mix
comprising
(1) a sleeve composition capable of providing a sleeve, and {2) a chemically
reactive
binder. The sleeves are cured in the presence of a catalyst by the cold-box or
no-bake
curing process. The invention also relates to a process for casting metal
parts using a
casting assembly where the sleeves are a component of the casting assembly.
to Additionally, the invention relates to the metal parts produced by the
casting process.
BACKGROUND OF THE INVENTION
A casting assembly consists of a pouring cup, a gating system (including
downsprues, choke, and runner), risers, sleeves, molds, cores, and other
components.
is To produce a metal casting, metal is poured into the pouring cup of the
casting assembly
and passes through the gating system to the mold and/or core assembly where it
cools
and solidifies. The metal part is then removed by separating it from the core
and/or
mold assembly.
The molds and/or cores used in the casting assembly are made of sand or other
2o Foundry aggregate and a binder, often by the no-bake or cold-box process.
The foundry
aggregate is mixed with a chemical binder and typically cured in the presence
of a liquid
or vaporous catalyst after it is shaped. Typical aggregates used in making
molds andlor
cores are aggregates having high densities and high thermal conductivity such
as are
silica sand, olivine, quartz, zircon sand, and magnesium silicate sands. The
amount of
2 s binder used for producing molds and/or cores from these aggregates on a
commercial
level is typically from 1.0 to 2.25 weight percent based upon the weight and
type of the
aggregate.
The density of a foundry mix is typically from 1.2 to 1.8 g/cc while the
thermal
conductivity of such aggregates typically ranges from 0.8 to 1.0 W/m.K. The
resulting
so molds and/or cores are not exothermic since they do not liberate heat.
Although molds
and cores have insulating properties, they are not very effective as
insulators. In fact,
molds and cores typically absorb heat.
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Risers or feeders are reservoirs which contain excess molten metal which is
needed to compensate for contractions or voids of metal which occur during the
casting
process. Metal from the riser fills such voids in the casting when metal from
the
casting contracts. Thus the metal from the riser is allowed to remain in a
liquid state for
s a longer period of time, thereby providing metal to the casting as it cools
and solidifies.
Sleeves are used to surround or encapsulate the riser and other parts of the
casting
assembly in order to keep the molten metal in the riser hot and maintain it in
the liquid
state. The temperature of the molten metal and the amount of time that the
metal in the
riser remains molten is a function of the sleeve composition and the thickness
of the
to sleeve wall, among other factors.
In order to serve their function, sleeves must have exothermic and/or
insulating
properties. The exothermic and insulating thermal properties of the sleeve are
different
in kind and/or degree than the thermal properties of the mold assembly into
which they
are inserted. Predominately exothermic sleeves operate by liberating heat
which satisfies
is some or all of the specific heat requirements of the riser and limits the
temperature loss
of the molten metal in the riser, thereby keeping the metal hotter and liquid
longer.
Insulating sleeves, on the other hand, maintain the molten metal in the riser
by insulating
it from the surrounding mold assembly.
Foundry molds and cores do not have the thermal properties which enable them
2o to serve the functions of a sleeve. They are not exothermic, are not
effective enough as
insulators, and absorb too much heat to keep the molten metal hot and liquid.
Compositions used in foundry molds and cores are not useful for making sleeves
because they do not have the required thermal properties and density.
Typical materials used to make sleeves are aluminum, oxidizing agents, fibers,
2s filers and refractory materials, particularly alumina, aluminosilicate, and
aluminosilicate
in the form of hollow aluminosilicate spheres. The type and amount of
materials in the
sleeve mix depends upon the properties of the sleeves which are to be made.
Typical
densities of sleeve compositions range from 0.4 g/ml to 0.8 g/ml. The thermal
conductivity for aluminum at room temperature is typically greater than 200
W/m.K
so while the thermal conductivity for hollow aIuminosilicate microspheres at
room '
temperature ranges from 0.05 W/m.K to 0.5 W/m.K. To some extent, all sleeves
are
required to have insulating properties, or combined insulating and exothermic
properties
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in order to minimize heat loss and to maintain the metal in a liquid state for
as long a
time as possible.
Three basic processes are used for the production of sleeves, "ramming",
~ "vacuuming", and "blowing or shooting". Ramming and blowing are basically
methods
s of compacting a sleeve composition and binder into a sleeve shape. Ramming
consists
Y
of packing a sleeve mix (sleeve composition and binder) into a sleeve pattern
made of
wood, plastic, and/or metal. Vacuuming consists of applying a vacuum to an
aqueous
slurry of a refractory and/or fibers and suctioning off excess water to form a
sleeve.
Typically, whether ramming, blowing, or vacuuming is used to form the sleeve,
the
sleeves formed are oven-dried to remove contained water and cure the sleeve.
If the
contained water is not removed, it may vaporize when it comes into contact
with the
hot metal and result in a safety hazard. In none of these processes is the
shaped sleeve
chemically cured with a liquid or vaporous catalyst.
These compositions are modified, in some cases, by the partial or complete
replacement of the fibers with hollow aluminosilicate microspheres. See PCT
publication WO 94/23865. This procedure makes it possible to vary the
insulating
properties of the sleeves and reduces or eliminates the use of fibers which
can create
health and safety problems to workers making the sleeves and using the sleeves
in the
casting process.
2o One of the problems with sleeves is that the external dimensions of the
sleeves
are not accurate. As a result, the external contour of the sleeves does not
coincide in
its dimensions with the internal cavity of the mold where the sleeve is to be
inserted. In
order to compensate for the poor dimensional accuracy, it is often necessary
to oversize
the cavity in the mold where the sleeve is to be inserted, or form or place
"crush ribs" in
2 s the mold assembly which erode or deform when the sleeves are inserted into
the riser
cavity to provide a means of locking the sleeve in place. Alternatively, the
sleeves are
placed in position on the casting pattern and the mold is made around the
sleeves, thus
avoiding problems with sleeves that are not dimensionally accurate.
Another problem with sleeves is that they may lack the required thermal
properties needed to maintain the molten metal in the riser reservoir in a hot
and liquid
state. The result is that the casting experiences shrinkage which results in
casting
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defects. These casting defects are most likely to be scrapped which results in
wasted
time and metal.
Runners, sprees, and other components of the casting assembly also can use
insulating and exothermic sleeves as coverings to maintain the temperature of
the molten
s metal which comes into contact with them.
SUMMARY OF THE INVENTION
This invention relates to a no-bake and cold-box process for making exothermic
and/or insulating sleeves, the sleeves made by this method, and the use of the
sleeves in
so making metal castings. Typically, the steps involved in preparing a sleeve
are:
(A) introducing a sleeve mix into a sleeve pattern to form an uncured sleeve
wherein said sleeve mix comprises:
~s (1) a sleeve composition capable of making a sleeve wherein the
sleeve composition comprises:
(a) an oxidizable metal and an oxidizing agent capable of
generating an exothermic reaction;
(b} an insulating refractory material; and
(c) mixtures of (a) and (b);
2s (2) an effective binding amount of a chemically reactive cold-box or
no-bake binder;
(B) contacting the uncured sleeve with a cold-box or no-bake catalyst to ,
allow the sleeves to become self supporting; and
.
(C} removing said sleeve from the pattern and allowing it to further cure and
become a hard, solid, cured sleeve.
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In the no-bake process, the curing catalyst is a liquid and is mixed with the
sleeve
composition, binder, and other components prior to shaping. In the cold-box
process,
the sleeve mix is first shaped and then contacted with a vaporous curing
catalyst. The
components of the no-bake and cold-box sleeve mixes can be uniformly mixed so
that
the mixture maintains its consistency, resulting in a sleeve where the
properties are
uniform throughout.
The no-bake and cold-box processes result in chemically cured sleeves. The
processes result in the higher production of sleeves per unit of time when
compared to
the processes known in the prior art. Additionally, there is less risk to the
health and
safety of workers who come into contact with the raw materials and sleeves
because
they are not exposed to any fibers which may cause breathing problems when
ingested
for prolonged periods of time.
The invention also relates to the sleeves produced by this process. The
sleeves
prepared by the process are dimensionally accurate. This allows for easy
insertion of the
sleeve into the mold. The riser sleeves can be inserted into the mold assembly
by
automatic methods, thereby further improving the productivity of the molding
process.
Since the density and thickness of the sleeve are more consistent and
dimensionally
accurate, the sleeves do not have to be oversized, nor is it necessary to use
"crush ribs"
or molds with ribs to keep the sleeve in place. Moreover, because the sleeves
are
2o sufficiently thermally stable, the castings made with casting assemblies
using the sleeves
do not contain shrinkage defects: This results in less scrap and greater
productivity.
The invention also relates to the casting of ferrous and non ferrous metal
parts
in a casting assembly of which the sleeves are a part, and to the parts made
by this
casting process. The casting made using these sleeves results in less waste
because the
25 sleeves enable the molten metal in the reservoir of the sleeve riser to be
reduced
compared to the molten metal contained in the reservoir of a sand riser
cavity.
Consequently, there is better utilization of the metal in the riser and this
allows for
additional castings to be made from the same amount of molten metal.
so BRIEF DESCRIPTION OF THE FIGURES
Figure 1 shows a casting assembly with two riser sleeves (side riser sleeve
and
top riser sleeve) inserted into the mold assembly of the casting assembly.
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Figure 2 graphically illustrates the effect of using a sleeve to keep the
molten
metal hot and liquid.
s Figure 3 shows a diagram representing a casting where shrinkage of the
casting
p
has occurred due to the inadequate thermal properties of the sleeve used. This
casting is
defective and will be scrapped as waste.
Figure 4 is a diagram showing a casting where there has been localized
shrinkage
lo of the metal riser, but no shrinkage of the casting. This localized
shrinkage does not
result in casting defects and waste.
DEFINITIONS
The following definitions will be used for terms in the disclosure and claims:
Casting assembly - assembly of casting components such as pouring cup,
downsprue,
gating system (downsprue, runner, choke), molds, cores, risers,
sleeves, etc. which are used to make a metal casting by pouring
molten metal into the casting assembly where it flows to the mold
2o assembly and cools to form a metal part.
Chemical binding - binding created by the chemical reaction of a catalyst and
a binder
which is mixed with a sleeve composition.
a s Cold-box - mold or core making process which utilizes a vaporous catalyst
to
cure the mold or core.
Downsprue - main feed channel of the casting assembly through which the ,
molten metal is poured.
30 "
EXACTCASTTM
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cold-box binder - a two part polyurethane-forming cold-box binder where the
Part
I is a phenolic resin similar to that described in U.S. Patent
3,485,797. The resin is dissolved in a blend of aromatic, ester,
~ and aliphatic solvents, and a silane. Part II is the polyisocyanate
s component comprises a polymethylene polyphenyl isocyanate, a
solvent blend consisting primarily of aromatic solvents and a
minor amount of aliphatic solvents, and a benchlife extender. The
weight ratio of Part I to Part II is about 55:45.
to EXACTCASTTM
no-bake binder - a two part polyurethane-forming no-bake binder which is
similar
to the EXACTCASTTM cold-box binder. EXACTCAST~'M no-
bake binder does not contain a benchlife extender or silane.
is Exothermic sleeve - a sleeve which has exothermic properties compared to
the
mold/core assembly into which it is inserted. The exothermic
properties of the sleeve are generated by an oxidizable metal
(typically aluminum metal) and an oxidizing agent which can react
to generate heat.
EXTENDOSPHERES SG -hollow aluminosilicate microspheres sold by PQ Corporation
having a particle size of 10-350 microns and an alumina content
between 28% to 33% by weight based upon the weight of the
microspheres.
EXTENDOSPHERES SLG -hollow aluminosilicate microspheres sold by PQ Corporation
having a particle size of IO-300 microns and an alumina content
of at least 40% by weight based upon the weight of the
' microspheres.
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Gating system - system through which metal is transported from the pouring cup
to the mold and/or core assembly. Components of the gating
system include the downsprue, runners, choke, etc.
s Handleable - sleeve which can be transported from one place to another
without sagging or breaking.
Insulating refractory
material - a refractory material with a thermal conductivity typically less
to than about 0.7 W/m.K at room temperature, preferably less than
about 0.5 W/m.K.
Insulating sleeve - a sleeve having greater insulating properties than the
mold/core
assembly into which it is inserted. An insulating sleeve typically
is contains low density materials such as fibers and/or hollow
microspheres.
Mold assembly - an assembly of molds and/or cores made from a foundry
aggregate (typically sand) and a foundry binder, which is placed
2o in a casting assembly to provide a shape for the casting.
No-bake - mold or core making process which utilizes a liquid catalyst to
cure the mold or core, also known as cold-curing.
Pouring cup - cavity into which molten metal is poured in order to fill the
2 s casting assembly.
Refractory - a ceramic type material, typically having a thermal conductivity
greater than about 0.8 W/m.K at room temperature, which is
capable of withstanding extremely high temperatures without
so essential change when it comes into contact with molten metal
which may have a temperature as high as, for instance, 1700°C. ,
Riser - cavity connected to a mold or casting cavity of the casting
assembly which acts as a reservoir for excess molten metal to
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prevent cavities in the casting as it contracts on solidification.
Risers may be open or blind. Risers are also known as feeders or
heads.
s Sleeve - any moldable shape having exothermic and/or insulating
properties made from a sleeve composition which covers, in
whole or part, any component of the casting assembly such as the
riser, runners, pouring cup, spree, etc. or is used as part of the
casting assembly. Sleeves can have a variety of shapes, e.g.
to cylinders, domes, cups, boards, cores.
Sleeve composition - any composition which is capable of providing a sleeve
with
exothermic and/or insulating properties. The sleeve composition
will usually contain aluminum metal and/or alucninosilicate,
15 ' particularly in the form of hollow aluminosilicate microspheres, or
mixtures thereof. Depending upon the properties wanted, the
sleeve composition may also contain alumina, refractories, an
oxidizing agent, fluorides, fibers, and fillers.
2o Sleeve mix - a mixture comprising a sleeve composition and a chemical
binder
capable of forming a sleeve by the no-bake or cold-box process.
W/m. K. - a unit of thermal conductivity = watt/meter Kelvin.
DETAILED DESCRIPTION OF FIGURES
Figure 1 shows a simple casting assembly comprising pouring cup I, spree 2,
runner 3, sleeve for side riser 4, side riser 5, sleeve for top riser 6, top
riser 7, and 8
mold and/or core assembly. Molten metal is poured into the pouring cup 1 where
it
flows through the spree 2 to the runner 3 and other parts of the gating
system,
3o ultimately to the 8 mold and core assembly. The risers 5, 7 are reservoirs
for excess
molten metal which is available when the casting cools, contracts and draws
molten
metal from the risers. The sleeves =t, G, which are inserted into the mold
and/or core
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assembly 8, surround the risers 5, 7, and keep the molten metal in the riser
reservoir
from cooling too rapidly.
Figure 2 graphically illustrates the beneficial effect of using a sleeve to
keep the '
s molten metal hot and liquid.
Figure 3 illustrates a casting 3 where there is shrinkage 2 of the metal of
the riser
1 and the metal of the casting 3. This casting is defective and will be
scrapped as waste.
to Figure 4 illustrates a casting 3 where there is shrinkage 2 of the metal of
the riser
1, but there is no shrinkage of the metal in the casting 3. This casting is
not defective
and can be used.
DESCRIPTION OF BEST MODE AND OTHER MODES
i5 FOR PRACTICING THE INVENTION
The sleeve mixes used in the subject process contain (1) a sleeve composition,
and (2) an effective amount of chemically reactive binder. The sleeve mix is
shaped and
cured by contacting the sleeve with an effective amount of a curing catalyst.
2o There is nothing novel about the sleeve composition used for making the
exothermic and/or insulating sleeves. Any sleeve composition known in the art
for
making sleeves can be used to make the sleeves. The sleeve composition
contains
exothermic and/or insulating materials, typically inorganic. The exothermic
and/or
insulating materials typically are aluminum-containing materials, preferably
selected from
2s the group consisting of aluminum metal, aluminosilicate, alumina, and
mixtures thereof,
most preferably where the aluminosilicate is in the form of hollow
microspheres.
The exothermic material is an oxidizable metal and an oxidizing agent capable
of
generating an exothermic reaction at the temperature where the metal can be
poured.
The oxidizable metal typically is aluminum, although magnesium and similar
metals can
3o also be used. The insulating material is typically alumina or
aluminosilicate, preferably
aluminosilicate in the form of hollow microspheres.
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When aluminum metal is used as the oxidizable metal for the exothermic sleeve,
it is typically used in the form of aluminum powder and/or aluminum granules.
The
oxidizing agent used for the exothermic sleeve includes iron oxide, maganese
oxide,
nitrate, potassium permanganate, etc. Oxides do not need to be present at
s stoichiometric levels to satisfy the metal aluminum fuel component since the
riser sleeves
and molds in which they are contained are permeable. Thus oxygen from the
oxidizing
agents is supplemented by atmospheric oxygen when the aluminum fuel is burned.
Typically the weight ratio of aluminum to oxidizing agent is from about 10:1
to about
2:1, preferably about S:I to about 4:1.
1o The thermal properties of the exothermic sleeve is enhanced by the heat
generated which reduces the temperature loss of the molten metal in the riser,
thereby
keeping it hotter and liquid longer. The exotherm results from the reaction of
aluminum
metal which has a thermal conductivity greater than 150 W/m.K at room
temperature,
more typically greater than 200 W/m.K. A mold and/or core does not exhibit
~s exothermic properties.
As was mentioned before, the insulating properties of the sleeve are
preferably
provided by hollow aluminosilicate microspheres, including aluminosilicate
zeeospheres.
The sleeves made with aluminosilicate hollow microspheres have low densities,
low
thermal conductivities, and excellent insulating properties. The thermal
conductivity of
2o the hollow aluminosilicate microspheres ranges from about 0.05 W/m.K to
about 0.6
W/m.K at room temperature, more typically from about 0.1 W/m.K to about 0.5
WIm.K.
The insulating and exothermic properties of the sleeve can be varied, but have
thermal properties which are different in degree andlor kind than the mold
assembly into
2s which they will be inserted.
Depending upon the degree of exothermic properties wanted in the sleeve, the
amount of aluminum in the sleeve will range from 0 weight percent to 50 weight
percent, typically 5 weight percent to 40 weight percent, based upon the
weight of the
sleeve composition.
3o Depending upon the degree of insulating properties wanted in the sleeve,
the
amount of hollow aluminosilicate microspheres, in the sleeve will range from 0
weight
percent to 100 weight percent, typically 40 weight percent to 90 weight
percent, based
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upon the weight of the sleeve composition. Since in most cases, both
insulating and
exothermic properties are needed in the sleeves, both aluminum metal and
hollow
aluminosilicate microspheres will be used in the sleeve. in sleeves where both
insulating
and exothermic properties are needed, the weight ratio of aluminum metal to
hollow
s aluminosilicate microspheres is typically from about 1:5 to about 1:1,
preferably from
about 1:1 to about 1:1.5.
The hollow aluminosilicate microspheres typically have a particle size of
about 3
mm. with any wall thickness. Preferred are hollow aluminosilicate microspheres
having
an average diameter less than 1 mm and a wail thickness of approximately 10%
of the
to particle size. It is believed that hollow microspheres made of material
other than
aluminosilicate, having insulating properties, can also be used to replace or
used in
combination with the hollow aluminosilicate microspheres.
The weight percent of alumina to silica (as Si02) in the hollow
aluminosilicate
microspheres can vary over wide ranges depending on the application, for
instance from
is 25:7 to 75:25, typically 33:67 to 50:50, where said weight percent is based
upon the
total weight of the hollow microspheres. It is known from the literature that
hollow
aluminosilicate microspheres having a higher alumina content are better for
making
sleeves used in pouring metals such as iron and steel which have casting
temperatures of
1300 °C to 1700 °C because hollow aluminosilicate microspheres
having more alurriina
2o have higher melting points. Thus sleeves made with these hollow
aiuminosilicate
microspheres will not degrade as easily at higher temperatures.
Refractories, although not necessarily preferred in terms of performance
because
of their higher densities and high thermal conductivities, may be used in the
sleeve
composition to impart higher melting points to the sleeve mixture so the
sleeve will not
2~ degrade when it comes into contact with the molten metal during the casting
process.
Examples of such refractories include silica, magnesia, alumina, olivine,
chromite,
aluminosilicate, and silicon carbide among others. These refractories are
preferably used
in amounts less than 50 weight percent based upon the weight of the sleeve
composition,
more preferably less than 25 weight percent based upon the weight of the
sleeve
3o composition. When alumina is used as a refractory, it is used in amounts of
less than
50% weight percent based upon the weight of the sleeve composition, more
preferably
less than 10% weight percent based upon the weight of the sleeve composition.
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CA 02221778 2001-11-07
The density of the sleeve composition typically ranges from about 0.1 g/cc to
about
0.9 g/cc, more typically from about 0.2 g/cc to about 0.8 g/cc. For exothermic
sleeves, the
density of the sleeve composition typically ranges from about 0.3 g/cc to
about 0.9 g/cc,
more typically from about U.5 g/cc to about 0.8 g/cc. For insulating sleeves,
the density of
the sleeve composition typically:ranges from about 0.1 g/cc to about 0.7 g/cc,
more typically
from about 0.3 g/cc to about 0.6 g/cc.
In addition, the sleeve composition may contain different fillers and
additives, such
as cryolite (Na3A1F6), potassium aluminum tetrafluoride, potassium aluminum
hexafluoride.
The binders that are mixed with the sleeve composition to form the sleeve mix
are
well known in the art. Any no-bake or cold-box binder, which will sufficiently
hold the
sleeve mix together in the shape of a sleeve and polymerize in the presence of
a curing
catalyst, will work. Examples of such binders are phenolic resins, phenolic
urethane
binders, furan binders, alkaline phenolic resole binders, and epoxy-acrylic
binders among
others. Particularly preferred are epoxy-acrylic and phenolic urethane binders
known as
EXACTCASTTM cold-box binders sold by Ashland Chemical Company. The phenolic
urethane binders are described in U.S. Patents 3,485,497 and 3,409,579. These
binders are
based on a two part system, one part being a phenolic resin component and the
other part
being a polyisocyanate component. The epoxy-acrylic binders cured with sulfur
dioxide in
the presence of an oxidizing agent are described in U.S. Patent 4,526,219.
The amount of binder needed is an effective amount to maintain the shape of
the
sleeve and allow for effective curing, i.e. which will produce a sleeve which
can be handled
or self supported after curing. An effective amount of binder is greater than
about 4 weight
percent, based upon the weight of the sleeve composition. Preferably the
amount of binder
ranges from about 5 weight percent to about 15 weight percent, more preferably
from about
6 weight percent to about 12 weight percent.
Curing the sleeve by the: no-bake process takes place by mixing a liquid
curing
catalyst with the sleeve mix (alternatively by mixing the liquid curing
catalyst with the
sleeve composition first), shaping the sleeve mix containing the catalyst, and
allowing the
sleeve shape to cure, typically al, ambient temperature without the addition
of heat. The
preferred liquid curing catalyst is a tertiary amine and the preferred no-bake
curing process
is described in U.S. Patent 3,485,797. Specific examples of such liquid curing
catalysts
13
CA 02221778 2001-11-07
include 4-alkyl pyridines wherein the alkyl group has from one to four carbon
atoms,
isoquinoline, arylpyridines such as phenyl pyridine, acridine, 2-
methoxypryridine,
pyridazine, 3-chloro pyridine, duinoline, N-methyl imidazole, N-ethyl
imidazole, 4,4'-
dipyridine, 4-phenylpropylpyridine, 1-methylbenzimidazole, and 1,4-thiazine.
Curing the sleeve by the cold-box process takes place by blowing or ramming
the
sleeve mix into a pattern and contacting the sleeve with a vaporous or gaseous
catalyst.
Various vapor or vapor/gas mixtures or gases such as tertiary amines, carbon
dioxide, methyl
formate, and sulfur dioxide can be used depending on the chemical binder
chosen. Those
skilled in the art will know which gaseous curing agent is appropriate for the
binder used.
For example, an amine vapor,~gas mixture is used with phenolic-urethane
resins. Sulfur
dioxide (in conjunction with an oxidizing agent) is used ith an epoxy-acrylic
resins, as
disclosed in U.S. Patent 4,526,219. Carbon dioxide (see U.S. Patent 4,985,489
which is
hereby incorporated into this disclosure by reference) or methyl esters (see
U.S. Patent
4,750,716 which is hereby incorporated into this disclosure by reference) are
used with
alkaline phenolic resole resins. Carbon dioxide is also used with binders
based on silicates,
as disclosed in IJ.S. Patent 4,391,642.
Preferably the binder is an EXACTCASTTM cold-box phenolic urethane binder
cured
by passing a tertiary amine gas, such as triethylamine, through the molded
sleeve mix in the
manner as described in U.S. Patent 3,409,579, or the epoxy-acrylic binder
cured with sulfur
dioxide in the presence of an oxidizing agent as described in U.S. Patent
4,526,219. Typical
gassing times are from 0.5 to 3.0 seconds, preferably from 0.5 to 2.0 seconds.
Purge times
are from 1.0 to 60 seconds, preferably from 1.0 to 10 seconds.
EXAMPLES
In all of the examples which follow, the binder used was either a no-bake or
cold-box
phenolic-urethane binder as specified where the ratio of Part I to Part II was
SS/45. The
sleeve mixes were prepared by mixing the sleeve composition and the binder in
a Hobart N.
SO mixer for about 2-4 minutes. In the no-bake sleeve compositions, the liquid
curing
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WO 97135677 PCTlUS97/04628
catalyst is added to the sleeve mix before shaping. The sleeves prepared were
cylindrical
sleeves 90 mm in internal diameter, 130 mm in external diameter, and 200 mm in
height.
The amount of binder used in all cases, except in Comparison Example A, was
8.8 weight
percent based upon the weight of the sleeve composition. All lettered Examples
are controls
s where silica sand was used as the sleeve composition. All parts are by
weight and all
percentages are weight percentages based upon the weight of the sleeve
composition unless
otherwise specified.
COMPARISON EXAMPLE A
to (Sleeve formed from silica sand.)
One hundred parts of silica sand were used as the sleeve composition which was
mixed with about 1.3 weight percent of EXACTCASTTM no-bake binder to form a
sleeve mix. Then about 1 weight percent of a liquid tertiary amine, POLYCAT 41
catalyst', sold by Air Products, is added to the sleeve mix. The resulting mix
is shaped
is into cylindrical sleeves.
The tensile properties of the sleeves, which indicates the strength of the
sleeves
for handling, are measured and set forth in Table I which follows. The tensile
strengths
of the sleeves are measured immediately (30 minutes), 1 hour, 4 hours, 24
hours, and 24
hours at 100% relative humidity (RIB after removing from the corebox.
2o Although the tensile strengths were good, steel castings made with the
sleeves
experienced shrinkage which is represented by Figure 3. The shrinkage occurred
because the thermal properties were not adequate for sleeve applications.
These
castings were defective and were scrapped.
2 s EXAMPLE 1
(Preparation of insulating sleeve by no-bake method)
The no-bake process of Comparison Example A was followed except 100 parts
of SG EXTENDOSPHERES were used as the sleeve composition and mixed with 8.8%
of EXACTCASTT~'I no-bake binder to form a sleeve mix. Then about 1 weight
percent
iLes s than 5.% active based upon die Part I.
CA 02221778 1997-11-21
WO 97/35677 PCT/US97/04628
of a liquid tertiary amine, POLYCAT 41 catalyst is added to the sleeve mix.
The
resulting mix is shaped into a sleeve.
The tensile properties of the sleeves, which indicates the strength of the
sleeves
for handling, are measured and set forth in Table I which follows. The tensile
strengths
s of the sleeves are measured immediately (30 minutes), I hour, 4 hours, 24
hours, and 24
hours at 100% relative humidity (R/-1] after removing from the corebox.
The sleeves are dimensionally accurate, both externally and internally.
EXAMPLE 2
to (Preparation of insulating sleeve containing hollow
aluminosilicate microspheres by cold-box method)
One hundred parts of SG EXTENDOSPHERES were used as the sleeve
composition and mixed with 8.8% of EXACTCASTTM cold-box binder to form a
sleeve
is mix. The sleeve mix of Example 1 is blown into a pattern having the shape
of a sleeve
and gassed with triethylamine in nitrogen at 20 psi according to known methods
described in U.S. Patent 3,409,579. Gas time is 2.5 second, followed by
purging with air at
60 psi for about 60.0 seconds.
The tensile strengths of the cured sleeves are measured as in Example 1 except
the
2o immediate tensile strength was measured 30 seconds after removing from the
corebox. The
tensile strengths of the sleeves are set forth in Table I. The sleeves are
dimensionally
accurate, both externally and internally.
EXAMPLE 3
as (Example 2 with silicone resin.)
Example 2 was followed except 1.2 weight percent of silicone resin was added
to the
sleeve mix. The tensile strength of the cured sleeves are measured as in
Example 2. The
tensile strengths of the sleeves are set forth in Table I. The sleeves are
dimensionally
accurate, both externally and internally. ,
EXAMPLE ~l
(Preparation of exothermic sleeve by the cold-box method.)
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WO 97/35677 PCT/US97/04628
The procedure ofExample 2 was followed except the sleeve composition used
consisted of 55% SLG EXTENDOSHPERES, 16.5% atomized aluminum, 16.5% aluminum
powder, 7% magnetite, and 5% cryolite. The tensile strengths of the cured
sleeves are
measured as in Example 2. The tensile strengths of the sleeves are set forth
in Table I.
The sleeves are dimensionally accurate, both externally and internally.
EXAMPLE 5
(Preparation of exothermic sleeve containing silica by the no-bake method.)
lo The procedure of Example 1 was followed except the sleeve composition used
consisted of 50% Wedron 540 silica sand, 10% alumina, and 40% of the sleeve
mix of
Example 4. The tensile strengths of the cured sleeves are measured as in
Example 1. The
tensile strengths of the sleeves are set forth in Table I. The sleeves are
dimensionally
accurate, both externally and internally.
EXAMPLE 6
(Preparation of exothermic sleeve containing silica by the cold-box method.)
The procedure of Example 2 was followed except the sleeve composition used
2o consisted of 50% Wedron 540 silica sand, 10% alumina, and 40% ofthe sleeve
mix of
Example 4. The tensile strengths of the cured sleeves are measured as in
Example 2. The
tensile strengths of the sleeves are set forth in Table I. The sleeves are
dimensionally
accurate, both externally and internally.
2 s EXAMPLE 7
(Sleeve composition.)
A sleeve composition is prepared by mixing the following components in a
Hobart N-50 mixer for about 4 minutes:
50% silica sand,
10% iron oxide,
10% alumina,
3% sodium nitrate,
m
CA 02221778 1997-11-21
WO 97/35677 PCT/US97/04628
20% aluminum powder, and
2% sawdust.
The sleeve composition is used to prepare cylindrical sleeves by the no-bake
or cold-box
method. Exothermic and insulating properties of the sleeves are varied by
changing the
amount of aluminum metal and alumina.
TABLE I
(Properties of Test Shapes)
TENSILE
STRENGTHS
OF
SLEEVES
E.1A.~~IPLESLEEVEImm. 1 hour4 hours 24 hourst~ 100% DIM. ACC.
RH
compa~;sonp 208 224 250 290 59 accurate
B
1 41 119 129 132 65 accurate
2 133 183 193 212 147 accurate
11 3 140 208 220 232 230 accurate
I2 5 88 69 I05 96 88 accurate
13 6 41 101 99 I29 70 accurate
14 7 99 140 106 144 125 accurate
EXAMPLES I S-20
In Comparison Example C, and Examples 15-20, the sleeves of Comparison
Example A and Examples 1-6 are tested in a casting assembly by using them to
surround
the top riser of the casting assembly. The metal poured into the casting
assembly is steel
(carbon content of 0.13%) and is poured at a temperature of 1650 °C.
The casting of
Comparison Example C, made using the sleeve from Comparison Example A,
experienced shrinkage and resulted in a defective casting which was scrapped
as waste.
The castings of Examples I S-20, made with sleeves 1-7, did not shrink as
Figure 4
illustrates. Figure 4 shows some shrinkage of the riser above the casting, but
there was
ao no shrinkage of the casting. In all cases, where the sleeves were made by
the cold-box
and no-bake process, there was no shrinkage of the casting. These results are
summarized in Table II which follows. '
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WO 97135677 PCT/US97/04628
TABLE II
CASTING RESULTS
EXAMPLE SLEEVE CASTII~fG RESiJLTS
ComparisonA Shrinkage of casting resulting in
C casting defect and waste.
15 1 No shrinkage of casting. No waste
or casting defect resulted.
16 2 No shrinkage of casting. No waste
or casting defect resulted.
17 3 No shrinkage of casting. No waste
or casting defect resulted.
1$ .f No shrinkage of casting. No waste
or casting defect resulted.
19 6 No shrinkage of casting. No waste
or casting defect resulted.
20 7 No shrinkage of casting. No waste
or casting defect resulted.
19
