Metal founding – Process – Shaping a forming surface
Patent
1995-10-26
1999-03-23
Bradley, P. Austin
Metal founding
Process
Shaping a forming surface
164525, 164526, 164528, 106 3835, 523139, B22C 122, B22C 900
Patent
active
058846883
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to the discovery of organometallic ceramic precursor binders used to fabricate shaped bodies by different techniques. Exemplary shape making techniques which utilize hardenable, liquid, organometallic, ceramic precursor binders include the fabrication of negatives of parts to be made (e.g., sand molds and sand cores for metalcasting, etc.), as well as utilizing ceramic precursor binders to make shapes directly (e.g., brake shoes, brake pads, clutch parts, grinding wheels, polymer concrete, refractory patches and liners, etc.). In a preferred embodiment, this invention relates to thermosettable, liquid ceramic precursors which provide suitable-strength sand molds and sand cores at very low binder levels and which, upon exposure to molten metalcasting exhibit low emissions toxicity as a result of their high char yields of ceramic upon exposure to heat.
BACKGROUND ART
The casting of metal articles using sand molds, sand shells and sand cores is well known in the art. Detailed information regarding the state of this technology can be found, for example, in a text by James P. LaRue, EdD, Basic Metalcasting, (The American Foundrymen's Society, Inc., Des Plaines, Ill., 1989, the subject matter of which is herein incorporated by reference). Using such a technique, a mold can be made from a mixture of sand and (typically) an organic binder by packing the mixture loosely or tightly around a pattern. The pattern is then removed, leaving a cavity in the sand which replicates the shape of the pattern. Once the organic binder is shape-stabilized by any of a number of hardening techniques (as described below), the cavities in the sand mold are filled with molten metal by pouring the molten metal into the mold.
In a typical shell molding operation, binder-coated sand can be blown onto the interior surface of a heated metal pattern. In a relatively short time (20-30 seconds) the heat from the pattern penetrates the sand, producing a bond in the heat-affected layer. This layer clings to the pattern, and when the pattern is rotated, the sand not affected by the heat falls into a hopper for further use. The thin, bonded layer of binder-coated sand clinging to the pattern is then cured by heating. The cured shell is then pushed from the pattern by ejector pins. When a mating shell is produced, the shells are aligned and fastened together with a high-temperature adhesive for pouring.
Just as the sand mold cavity provides the external shape of a casting, any holes or other internal shapes in a casting can be produced by using sand cores. When such cores are made from sand, numerous acceptable processes for making these cores are acceptable. In most cases, a sand mixture comprising a binder material is placed into a corebox. There, the sand mixture takes the shape of the cavity in the box, becomes hard, and is removed. After the mold is made, the core is then set in the "drag" just before the mold is closed. When the metal is poured, the molten metal fills the mold cavity except for where sand cores are present. Thus, the shape of the solidified casting results from the combined shapes of the mold and the sand core(s).
Before 1943, coremaking was simple. There was one core process, known as oil-sand, which had been used for many years. Since then, there has been a dramatic increase in coremaking technology. At present there are at least 21 different coremaking systems. Over 160 binder materials are now available for making cores. These binder materials can be categorized as vapor-cured (cured by a gas of some kind), heat-cured (cured by heat), or no-bake (cured by chemical reaction).
While it is not the intent of this disclosure to discuss all of the various binders which are currently in use for such processes, perhaps the most commonly utilized binders comprise both inorganic and organic resins.
In the realm of inorganic systems, both vapor-cured and no-bake sodium silicate binders are known. No-bake, oxide-cured phosphate binders are also available. Such inorganic binders often have l
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Hinton Jonathan Wayne
Jensen James Allen
Lukacs III Alexander
Boland Kevin J.
Bradley P. Austin
Knapp Jeffrey T.
Lanxide Technology Company, LP
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