Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-03-21
2002-01-01
Fuelak, Morion (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C521S054000, C523S218000, C164S527000
Reexamination Certificate
active
06335387
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to insulating sleeve compositions comprising (1) a major mount of hollow aluminosilicate microspheres, and (2) fine silica The sleeve compositions are used to form sleeve mixes by mixing them with a chemically reactive binder. Sleeves are formed from the sleeve mix and 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. 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. 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.
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 a longer period, 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 are a function of the sleeve composition and the thickness of the sleeve wall, among other factors.
Typical materials used to make sleeves are aluminum, oxidizing agents, fibers, fillers 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 that are to be made, particularly the insulating and exothermic properties of the sleeve.
Three basic processes are used for the production of sleeves, “ramming”, “vacuuming”, and “blowing or shooting”. Ramming and blowing are methods of compacting a sleeve composition and binder into a sleeve shape. Ramming consists 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, when 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 is exposed to the hot metal and result in a safety hazard.
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. WO 98/03284 discloses a cold-box and no-bake process for making sleeves with certain hollow aluminosilicate microspheres.
One property of sleeves that is of major concern is the safety margin of the sleeve. The safety margin is the distance from the top of the casting surface to the shrinkage cavity within the riser. A positive value indicates that all shrinkage was confined to the riser and the casting was sound. A negative value indicates that shrinkage extended into the casting. The safety margin can be measured in inches or as a percentage of the total height of the original riser. Generally, values that are more positive indicate better performance. There is a continuous interest in developing sleeves with an increased safety factor.
SUMMARY OF THE INVENTION
This invention relates to insulating sleeve compositions comprising:
(1) a major amount of hollow aluminosilicate microspheres, and
(2) fine silica.
The sleeve compositions are used to form sleeve mixes by mixing them with 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.
The addition of small amounts of fine silica to the sleeve composition improves the insulating properties and safety margin of insulating riser sleeves made from the sleeve compositions and an organic binder. The surface finish of castings, made with casting assemblies where the insulating sleeves are inserted, is also improved.
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 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.
Cold-box—mold or core making process, which uses a vaporous catalyst to cure resins, used to make the mold or core.
ISOCURE® 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, and 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.
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 in a casting assembly to provide a shape for the casting.
No-bake—mold or core making process which uses a liquid catalyst to cure the mold or core, also known as cold-curing.
Riser—cavity connected to a mold or casing cavity of the casting assembly, which acts as a reservoir for excess molten metal to prevent cavities in the casting as it contacts on solidification. Risers may be open or blind. Risers are also known as feeders or heads.
Safety margin—distance from the top of the casting surface to the shrinkage cavity within the riser. A positive value indicates that all shrinkage was confined to the riser and the casing was sound. A negative value indicates that shrinkage extended into the casting. The safety margin can be measured in inches or as a percentage of the total height of the original riser. Generally, values that are more positive indicate better performance.
SGT—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.
GT—hollow aluminosilicate microspheres sold by PQ Corporation having a particle size of 10-350 microns and an alumina content between 24% to 30% by weight based upon the weight of the microspheres.
SLG—hollow aluminosilicate microspheres sold by PQ Corporation having a particle size of 10-300 microns and an alumina content of about 40% by weight based upon the weight of the microspheres.
Sleeve—any moldable shape having exothermic an
Aufderheide Ronald C.
Twardowska Helena
Ashland Inc.
Fuelak Morion
Hedden David L.
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