U.S. patent application number 10/919149 was filed with the patent office on 2005-01-27 for process for casting a metal.
This patent application is currently assigned to Ashland Inc.. Invention is credited to Aufderheide, Ronald C., Massey, William J., Showman, Ralph E..
Application Number | 20050016711 10/919149 |
Document ID | / |
Family ID | 29734036 |
Filed Date | 2005-01-27 |
United States Patent
Application |
20050016711 |
Kind Code |
A1 |
Aufderheide, Ronald C. ; et
al. |
January 27, 2005 |
Process for casting a metal
Abstract
This invention relates to an improved process for casting a
metal by pouring molten metal into and around a mold assembly,
where a riser is a component of the mold assembly. The process
comprises (a) inserting a riser insert into the cavity of the
riser, and (b) then allowing molten metal to flow into the cavity
of the riser containing the riser insert. The process is carried
out in a manner such that the density and the shape of the riser
insert enables the riser insert to float on the surface of the
molten metal when the molten metal enters the cavity of the
riser.
Inventors: |
Aufderheide, Ronald C.;
(Dublin, OH) ; Showman, Ralph E.; (Galloway,
OH) ; Massey, William J.; (Pataskala, OH) |
Correspondence
Address: |
David L. Hedden
Ashland Inc.
P.O. Box 2219
Columbus
OH
43216
US
|
Assignee: |
Ashland Inc.
|
Family ID: |
29734036 |
Appl. No.: |
10/919149 |
Filed: |
August 16, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10919149 |
Aug 16, 2004 |
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10176027 |
Jun 20, 2002 |
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Current U.S.
Class: |
164/359 ;
164/137 |
Current CPC
Class: |
B22C 9/088 20130101 |
Class at
Publication: |
164/359 ;
164/137 |
International
Class: |
B22C 009/08; B22D
033/04 |
Claims
1. A process, for forming a metal casting by pouring molten metal
into and around a casting assembly comprising an open riser having
a cavity, wherein said process comprises: (a) inserting a
low-density riser insert comprised of hollow aluminosilicate
microspheres having a density of from about 0.3 g/cc to about 1.6
g/cc into the cavity of the riser low-density riser insert
comprised of hollow aluminosilicate microspheres into the cavity of
the riser, and (b) then allowing molten metal to flow into the
cavity of the riser containing the riser insert, wherein, the riser
is shaped such that, or contains a barrier such that, the riser
insert does not fall into other parts of the casting assembly
before the molten metal is poured, and the density of the riser
insert is such that the riser insert floats on the surface of the
molten metal when the molten metal enters the cavity of the
riser.
2. The process of claim 1 where the riser insert acts as a barrier
to heat loss from the metal in the riser by radiation and/or
convection to the atmosphere.
3. The process of claim 2 wherein the riser insert has insulating
properties, exothermic properties, or both.
4. The process of claim 3 wherein the riser is a component of a
casting assembly.
5. (canceled)
6. The process of claim 6 4 where the riser contains a physical
barrier to keep the riser insert in the riser and prevent the riser
insert from falling out.
7. The process of claim 6 wherein the riser contains a breaker core
or is a neckdown riser.
8. The process of claim 7 wherein the riser insert retains
insulating properties until the metal in riser solidifies.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not Applicable.
CLAIM TO PRIORITY
[0002] Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0003] Not Applicable.
REFERENCE TO A MICROFICHE APPENDIX
[0004] Not Applicable.
BACKGROUND OF THE INVENTION
[0005] (1) Field of the Invention
[0006] This invention relates to an improved process for casting a
metal by pouring molten metal into and around a casting assembly,
where a riser is a component of the casting assembly. The process
comprises (a) inserting a riser insert into the cavity of the
riser, and (b) then allowing molten metal to flow into the cavity
of the riser containing the riser insert. The density of the riser
insert is such that the riser insert floats above the surface of
the molten metal when the molten metal enters the cavity of the
riser and provides a thermal barrier to reduce heat loss from the
riser.
[0007] (2) Description of the Related Art
[0008] A casting assembly typically consists of a pouring cup, a
gating system (including downsprues, choke, and runner), risers,
molds, cores, and other components. 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.
[0009] The molds and/or cores used in the casting assembly are
typically made of sand and a binder, often by the no-bake or
cold-box process. The sand is mixed with a chemical binder and
typically cured in the presence of a liquid or vaporous catalyst
after it is shaped.
[0010] Risers are cavities in which excess molten metal flows. The
excess molten metal is needed to compensate for contractions or
shrinkage of metal, which occur during the casting process. Metal
from the riser fills such voids created in the casting when metal
from the casting contracts. The metal from the riser must remain in
a liquid state for a longer period of time, so it can provide
molten metal to the casting as it cools and solidifies. Thus, it is
advantageous to keep the molten metal in the riser hot as long as
possible.
[0011] Heat loss from the riser occurs by convection to the cooler
surroundings and through radiation to the cooler atmosphere.
Because of this problem with heat loss associated with open risers,
closed risers, which are surrounded by and covered with sleeve
material are risers is that the operator cannot see when the riser
cavity is full by visual inspections. In addition, closed risers do
not provide venting of mold gasses to the atmosphere during
pouring. These conditions can result in over-filling of the mold,
metal spillage, and resulting safety hazards.
[0012] Because of the problems associated with using closed risers,
open risers are sometimes preferred. When an open riser is used,
the operator can visually inspect the riser cavity and determine
when the level of molten metal in the riser cavity is appropriate.
After the appropriate level is reached, in order to prevent heat
loss from an open riser, the top of the riser cavity is covered
with a hot-topping, e.g. a granular material, a powder, rice hulls,
a blanket (see U.S. Pat. No. 3,876,420), and solid covers
(graphite) having an insulating properties, exothermic properties,
or both, within a relatively short period of time to prevent
excessive heat loss. When an open riser is used, typically,, an
extra person is needed to inspect the riser cavity and apply the
topping following pouring.
[0013] If the hot-topping is a granular or powder material, it
often spills across the top of the casting assembly onto the floor
of the foundry. Because there is often spillage or misapplication,
it is normal practice to apply much more than the optimum amount
that is necessary. Additionally, when powdered materials are used,
the powdered materials can miss the top of the riser and spill onto
the casting assembly where it can eventually get mixed into the
molding sand and consequently cause casting defects.
[0014] If blankets are placed on top of the riser, before the riser
is filled with metal, the metal pourer is not able to see the metal
fill the riser and the molten metal could overflow and spill onto
the floor. If blankets are placed on the riser after the
appropriate level of molten metal is reached, an extra person is
usually required to inspect the riser cavity and to place the
blanket on top of the open riser while the metal pourer moves on to
pour the next mold. Furthermore, the metal in the riser is open to
the atmosphere during the time between filling and when the blanket
is applied, which results in heat loss. The longer the delay before
the cover is placed over the cavity, the more heat is lost and the
effectiveness of the riser is reduced.
[0015] All citations referred to under this description of the
"Related Art" and in the "Detailed Description of the Invention"
are expressly incorporated by reference.
BRIEF SUMMARY OF THE INVENTION
[0016] This invention relates to an improved process for casting a
metal by pouring molten metal into and around a mold
assembly,.where a riser is a component of the mold assembly. The
process comprises (a) inserting a riser insert into the cavity of
the riser, and (b) then allowing molten metal to flow into the
cavity of the riser containing the riser insert. The process is
carried out in a manner such that the density and the shape of the
riser insert enables the riser insert to float on the surface of
the molten metal when the molten metal enters the cavity of the
riser. When the molten metal enters the riser cavity, the shaped
material floats on top of the molten metal and, thereby, prevents
the heat of the molten metal from escaping.
[0017] The riser insert is slightly smaller than the internal cross
section of the riser, so the riser insert can be easily dropped or
inserted into the riser. In order to prevent the riser insert from
falling through the riser cavity into other parts of the casting
assembly, the bottom of the riser is shaped as a breaker core or
the neckdown portion of a neckdown riser. Alternatively, a barrier,
e.g. a nail, rod, foam filler, filter cloth, or fin, is inserted
into the riser cavity below the riser insert, which prevents the
riser insert from falling into other parts of the casting
assembly.
[0018] There are many advantages to the subject process. Certainly,
one of the major advantages is that the loss of heat is minimized
from the time the pour begins, because the riser insert is present
before the pouring begins. Furthermore, the metal pourer can see
the riser insert rising, so he knows when the riser is filled and,
thus, avoids over filling the mold. Because the riser insert can be
placed in the riser before the metal is poured, extra manpower is
not needed to cover the riser cavity when the riser cavity is
filled with molten metal. Additionally, because the riser insert is
in the riser while the casting assembly is setting before the
molten metal is poured, it prevents dirt from falling through the
riser cavity into the casting assembly. This problem is of
particular concern when casting larger parts, where the pour is
delayed for several hours or even days after the casting assembly
is arranged. If dirt gets into the mold, it must be removed, or
casting defects are likely to result. The removal of dirt involves
extra time and money. The riser insert can be properly sized to
provide the optimum insulating and/or exothermic properties without
the use of excessive material and without the under application of
materials and excessive heat loss.
[0019] FIGS. 9 and 10 illustrate further advantages of this
invention. FIGS. 9 and 10 show the performance of a riser which is
covered by traditional hot topping material (FIG. 9) compared to
using a floating riser insert (FIG. 10). The floating riser insert
keeps the top of the riser liquid longer and prevents the formation
of the layer of solidified metal skin that forms on the top of the
riser when a hot topping material is used.
[0020] The formation of a skin on top of a riser can prevent the
atmospheric pressure from getting inside the riser so it can push
on the remaining liquid metal. This is why the design of blind
risers incorporates a "firecracker" (Williams) core that creates a
hot spot at the top of the riser. This helps keep the top open and
allows the atmospheric pressure to push the liquid metal into the
shrinking casting cavity. Test results indicate that the floating
riser insert may also be used in a blind riser application and
could eliminate the need for the firecracker core.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0021] FIG. 1 Is a copy of a photograph showing the top of a mold
with an open riser before the riser insert is added.
[0022] FIG. 2 Is a copy of a photograph showing the top of a mold
where a riser insert was placed into the open riser and settled in
a vertical position.
[0023] FIG. 3 Is a copy of a photograph showing the top of a mold
where a riser insert was placed into the open riser and settled in
a horizontal position.
[0024] FIG. 4 Is a copy of a photograph showing the pouring of
metal into the mold which contained the vertical positioned insert
and the insert floating on top of the raising metal in the
riser.
[0025] FIG. 5 Is a copy of a photograph showing the top of a mold
with the insert covering the top of the open riser after the metal
was poured.
[0026] FIG. 6 Is a copy of a photograph showing the pouring of
metal into the mold which contained the horizontal positioned
insert and the insert floating on top of the raising metal in the
riser.
[0027] FIG. 7 Is a copy of a photograph showing the top of a mold
where an exothermic insert was used and the exothermic insert
igniting after the filling of the mold.
[0028] FIG. 8 Is a copy of a photograph showing the top of the
molds after the metal was poured.
[0029] FIG. 9 Is a copy of a photograph showing a cross-section of
a riser where a traditional exothermic hot topping was used to
cover the top of the riser after the mold was poured.
[0030] FIG. 10 Is a copy of a photograph showing a cross-section of
a riser where an exothermic floating riser insert was used in place
of hop topping to cover the top of the riser before the mold was
poured.
DETAILED DESCRIPTION OF THE INVENTION
[0031] The detailed description and examples will illustrate
specific embodiments of the invention and will enable one skilled
in the art to practice the invention, including the best mode. It
is contemplated that many equivalent embodiments of the invention
will be operable besides these specifically disclosed.
[0032] For purposes of describing this invention, a "riser insert"
is a shape; typically a circular disk, which fits into a riser
cavity and will float on top of the molten metal when it enters the
riser cavity. The riser is shaped so that the riser insert will not
fall through the riser into other parts of the casting assembly, or
the riser contains a barrier that prevents the riser insert from
falling through the riser cavity to other parts of the casting
assembly.
[0033] When the metal, is poured and fills the riser, the riser
insert floats, on top of the molten metal. To float, the riser
insert must be made of a material that has a density lower than
that of the metal being poured. The riser insert can be made from a
variety of materials, e.g. ceramic fiber-based refractories,
granular refractories, sand, microsphere refractories, paper,
cardboard, etc. It is possible to use materials that turn when
exposed to the heat of the molten metal, provided the material
stays in place while the metal cools to prevent the loss of heat
from the riser. It is even possible to use paper or cardboard if
treated with fire retardant materials, so the paper burns slower.
The ashes that are left create an insulating barrier between the
top of the riser and the air above the mold.
[0034] The riser insert is preferably used with an open riser (one
that has a top that is open to the atmosphere), preferably an open
riser that has a breaker core on the bottom or is a neckdown type
riser where the bottom of the riser where it contacts the casting
is smaller than the upper section of the riser. These types of
risers will naturally keep the riser insert from falling down into
the casting cavity.
[0035] In practice the riser insert is typically placed in the
riser cavity when the mold is assembled. This eliminates the need
for a person at the pouring area to place toppings or blankets on
the molds after they are poured.
[0036] Insulating or exothermic hot-topping is typically applied on
top of the liquid metal in the riser after the mold has been
poured. The application of the hot-topping needs to occur within a
relatively short period of time to prevent excessive heat loss.
This typically dictates that a second person is needed to follow
the pourer to apply the topping. The hot-topping material is
typically a granular or powder material that is applied by volume
and may or may not be measured. The material often spills across
the top of the mold or on the floor. To allow for spillage or
misapplication, it is normal practice to apply much more than the
optimum amount.
[0037] Preferably used to make the riser inserts are low density
microspheres. Riser inserts made with low-density microspheres are
dimensional accurate and maintain their dimensional important
because the dimensionally accurate riser inserts do not stick in
the riser cavity, and, consequently, are free floating. Riser
inserts made from these materials have thermal conductivities about
1/4 the thermal conductivities of corresponding riser inserts made
from sand and they provide better insulating characteristics.
Furthermore, because they are light-weight and have a low-density,
they are easy to handle and provide the maximum buoyant force to
insure that the riser insert floats to the top of the riser cavity
when the molten metal is poured.
[0038] Examples of microspheres include hollow aluminosilicate
microspheres, including aluminosilicate zeospheres. The riser
inserts made with aluminosilicate hollow microspheres have low
densities, low thermal conductivities, and excellent insulating
properties. The thermal conductivity of the hollow aluminosilicate
microspheres ranges from about 0.1 W/m.K to about 0.6 W/m.K at room
temperature, more typically from about 0.15 W/m.K to about 0.4
W/m.K.
[0039] The hollow aluminosilicate microspheres used to make the
riser inserts typically have a particle size of about 10 to 350
microns with varying wall thickness. Preferred are hollow
aluminosilicate microspheres having an average diameter greater
than 150 microns and a wall thickness of approximately 10% of the
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.
[0040] The weight percent of alumina to silica (as SiO.sub.2) in
the hollow aluminosilicate microspheres can vary over wide ranges
depending on the application, for instance from 25:75 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 that
hollow aluminosilicate microspheres having a higher alumina content
are better for making larger riser inserts used in pouring metals
such as iron and steel which have casting temperatures of
1300.degree. C. to 1700.degree. C., because hollow aluminosilicate
microspheres having more alumina have higher melting points. Thus
riser inserts made with these hollow aluminosilicate microspheres
will not degrade as easily at higher temperatures.
[0041] The density of the riser insert typically ranges from about
0.3 g/cc to about 1.6 g/cc, more typically from about 0.4 g/cc to
about 0.6 g/cc.
[0042] In some cases, it is desirable to have a riser insert having
exothermic properties, in order to supply additional heat to the
molten metal in the riser cavity. Riser inserts are rendered
exothermic by the addition of an oxidizable metal and an oxidizing
agent to the formulation used to make the riser insert. The
oxidizing agent is capable of generating an exothermic reaction
when it comes into contact with the molten metal poured. The
oxidizable metal typically is aluminum, although magnesium and
similar metals can also be used.
[0043] When aluminum metal is used as the oxidizable metal for the
exothermic riser insert, it is typically used in the form of
aluminum powder and/or aluminum granules. The oxidizing agents used
for the exothermic riser insert includes iron oxide, manganese
oxide, etc. Oxides do not need to be present at stoichiometric
levels to satisfy the metal aluminum fuel component since the riser
inserts 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 5:1 to about 2.5:1.
[0044] The thermal properties of the exothermic riser insert are
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 typical exotherm in sleeves and sleeve related
products results from the oxidizing reaction of aluminum metal. A
mold and/or core typically does not exhibit exothermic
properties.
[0045] In addition, the riser insert formulation may contain
different fillers and additives, such as cryolite
(Na.sub.3AlF.sub.6), potassium aluminum tetrafluoride, potassium
aluminum hexafluoride, nitrates, paper, wood flour, sand, etc.
[0046] The binders that are used to hold the riser insert
composition together are well known in the foundry art. Any
no-bake, cold-box binder, oil sand, or shell resin, which will
sufficiently hold the riser insert composition together in the
shape of a riser insert 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, acid curable shell resins based upon phenolic novolac
resins, and e.g. epoxy-acrylic binders among others. Particularly
preferred are epoxy-acrylic binders (e.g. ISOSET.RTM. binders sold
by Ashland Specialty Chemical, a division of Ashland Inc.),
epoxy-acrylic-isocyanate binders e.g. ISOMAX.RTM. binders sold by
Ashland Specialty Chemical, a division of Ashland Inc.), and
phenolic urethane binders (e.g. EXACTCAST.TM. and ISOCURE.RTM.
binders sold by Ashland Specialty Chemical, a division of Ashland
Inc.) cold-box binders. The phenolic urethane binders are described
in U.S. Pat. Nos. 3,485,497 and 3,409,579, which are hereby
incorporated into this disclosure by reference. 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. Pat. No. 4,526,219,
which is hereby incorporated into this disclosure by reference. The
epoxy-acrylic-isocyanate binders, cured with a volatile amine are
described in U.S. Pat. No. 5,688,837, which is hereby incorporated
into this disclosure by reference.
[0047] The amount of binder needed is an effective amount to
maintain the shape of the riser insert and allow for effective
curing, i.e. which will produce a riser insert which can be handled
or self-supported after curing. An effective amount of binder will
vary greatly depending upon the materials used to make the insert
and can range from 0.8% to 14% based on the weight of the insert
composition. Preferably the amount of binder ranges from about 1
weight percent to about 12 weight percent.
[0048] Curing the riser insert by the no-bake process takes place
by mixing a liquid curing catalyst with the riser insert mix
(alternatively by mixing the liquid curing catalyst with the riser
insert composition first), shaping the riser insert mix containing
the catalyst, and allowing the riser insert shape to cure,
typically at 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. Pat. No.
3,485,797, which is hereby incorporated by reference into this
disclosure. Specific examples of such liquid curing catalysts
include 4-alkyl pyridines wherein the alkyl group has from one to
four carbon atoms, isoquinoline, arylpyridines such as phenyl
pyridine, pyridine, acridine, 2-methoxypyridine, pyridazine,
3-chloro pyridine, quinoline, N-methyl imidazole, N-ethyl
imidazole, 4,4'-dipyridine, 4-phenylpropylpyridine,
1-methylbenzimidazole, and 1,4-thiazine.
[0049] Curing the riser insert by the cold-box process takes place
by blowing or ramming the riser insert mix into a pattern and
contacting the riser insert with a vaporous or gaseous catalyst.
Various vapor or vapor/gas mixtures or gases such as tertiary
amines, carbon dioxide, methyl format, 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 with an epoxy-acrylic resins. See U.S.
Pat. No. 4,526,219, which is hereby incorporated, into this
disclosure by reference. Carbon dioxide (see U.S. Pat. No.
4,985,489, which is hereby incorporated into this disclosure by,
reference) or methyl esters (see U.S. Pat. No. 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. See U.S. Pat. No. 4,391,642, which
is hereby incorporated, into this disclosure by reference.
[0050] Preferably the binder is an ISOCURE.RTM. cold-box phenolic
urethane binder cured by passing a tertiary amine gas, such as
triethylamine, through the molded riser insert mix in the manner as
described in U.S. Pat. No. 3,409,579, or the epoxy-acrylic binder
cured with sulfur dioxide in the presence of an oxidizing agent as
described in U.S. Pat. No. 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.
ABBREVIATIONS
[0051] The following abbreviations are used:
[0052] Casting assembly--assembly of casting components such as
pouring cup, downsprue, gating system (downsprue, runner, choke),
molds, cores, risers, riser inserts, etc. which are used to make a
metal casting by pouring molten metal into the casting assembly
where it flows to the mold assembly and cools to form a metal
part.
[0053] Cold-box--mold or core making process which utilizes a
vaporous catalyst to cure the mold or core.
[0054] Downsprue--main feed channel of the casting assembly through
which the molten metal is poured.
[0055] EXACTCAST.RTM. 101/202
[0056] 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. Pat. No. 3,485,797. The resin is dissolved in a
blend of aromatic, ester, and aliphatic solvents, and a silane.
Part II is the polyisocyanate component comprising 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.
[0057] SGT--hollow aluminosilicate microspheres sold by PQ
Corporation under the EXTENDOSPHERE trademark 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.
[0058] SLG--hollow aluminosilicate microspheres sold by PQ
Corporation EXTENDOSPHERE trademark having a particle size of
10-300 microns and an alumina content of at least 40% by weight
based upon the weight of the microspheres.
[0059] 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.
[0060] Mold assembly an assembly of molds and/or cores made from a
foundry aggregate (typically sand) and a foundry binder, which is
placed in and/or around a casting assembly to provide a shape for
the casting.
[0061] No-bake--mold or core making process which utilizes a liquid
catalyst to cure the mold or core, also known as cold-curing.
[0062] Pouring cup--cavity into which molten metal is poured in
order to fill the casting assembly.
[0063] Riser--cavity connected to a mold or casting cavity of the
casting assembly which acts as a reservoir for excess molten metal
to prevent cavities in the casting as it contracts on
solidification. Risers may be open or closed to the atmosphere.
EXAMPLES
[0064] While the invention has been described with reference to a
preferred embodiment, those skilled in the art will understand that
various changes may be made and equivalents may be substituted for
elements thereof without departing from the scope :of the
invention. In addition, many modifications may be made to adapt a
particular situation or material to the teachings of the invention
without departing from the essential scope thereof. Therefore, it
is intended that the invention not be limited to the particular
embodiment disclosed as the best mode contemplated for carrying out
this invention, but that the invention will include all embodiments
falling within the scope of the appended claims. In this
application all units are in the metric system and all amounts and
percentages are by weight, unless otherwise expressly
indicated.
Examples 1-2
[0065] (Preparation of Disk-Shaped Riser Inserts)
[0066] An insulating and exothermic disk-shaped riser inserts were
prepared. The formulation for the insulating disk-shaped riser
insert consisted of a blend of SGT and SLG microspheres, 6% boric
acid, and 9% EXACTCAST.RTM. 101/201 cold-box binder sold by Ashland
Specialty Chemical Company, a division of Ashland Inc. The
formulation for the exothermic disk-shaped riser insert consisted
of approximately 60% SGT microspheres, 9% ISOCURE 101/201 binder,
and 31% "thermite" (a mixture of powdered aluminum, iron oxide, and
igniters). The disk-shaped riser inserts were prepared by blowing
the formulations into a breaker core pattern with the inserts
removed to create disks that were approximately 31/4" in diameter
by 3/8" thick. The pattern was then gassed with triethylamine in
nitrogen at 20 psi according to known methods described in U.S.
Pat. No. 3,409,579. Gas time is 0.5 seconds second, followed by
purging with air at 20 psi for about 15 seconds.
Example 3-4
[0067] Use of the Riser Inserts of Examples 1-2 in a Riser)
[0068] The disk-shape riser inserts of Examples 1-2 were dropped
into a four-inch open riser with a breaker core, which was part of
a "penetration" test casting assembly. FIGS. 2 and 3 show the
insulating and exothermic riser inserts respectively placed in the
riser sleeve before the castings were poured. One of the
disk-shaped riser inserts was intentionally placed in the vertical
position (see FIG. 2) and the other was place in a horizontal
position (see FIG. 3). Molten gray iron, having a temperature of
approximately 1480.degree. C. was poured into and around the test
casting assembly.
[0069] Both of the disk-shaped riser inserts floated in the riser
cavities as the riser cavity filled, so that at the end of the
pouring, the disk-shaped inserts were on the top of the liquid
metal at the cope surface of the mold. After approximately 20
seconds after pouring, the exothermic disk-shaped riser insert
ignited to provide additional heat.
* * * * *