Metal founding – Process – Shaping liquid metal against a forming surface
Reexamination Certificate
2000-11-14
2002-06-25
Lin, Kuang Y. (Department: 1722)
Metal founding
Process
Shaping liquid metal against a forming surface
C164S485000
Reexamination Certificate
active
06408931
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the continuous casting of molten metal, e.g. aluminum and its alloys, into ingots of indeterminate length. More specifically, this invention relates to methods of making molds for continuous casting of molten metals and to the construction of such molds.
BACKGROUND OF THE INVENTION
Continuous casting of molten metals into ingots of any desired length is well-known and many molds to permit continuous casting of, for example, aluminum and aluminum alloys have been described in the art.
Wagstaff, et. al., in U.S. Pat. No. 3,688,834, Sep. 5, 1972, describe one mold construction for continuous casting of molten metals, this patent being directed to the inherent problem of thermal warpage of the mold arising from temperature differentials. Since, portions of the mold are water cooled and portions of the mold are in contact with the molten metal thermal warpage is inherent in the structure.
Wagstaff, et. al. for over a quarter century have been designing and improving molds for continuous casting of molten metals. The above-mentioned patent and those referred to hereinafter are incorporated herein as representing the development of the art and the present state of the art. The following Wagstaff, et. al., United States patents are incorporated by reference: U.S. Pat. No. 3,739,837, Jun. 19, 1973, (cooling chamber construction); U.S. Pat. No. 4,598,763, Jun. 8, 1986 (directly cooled, unitary annular graphite casting ring); U.S. Pat. No. 4,693,298, Sep. 15, 1987, (controlling direct cooling rate of graphite in continuous casting of molten metal); U.S. Pat. No. 4,947,925 (direct cooling of graphite casting ring made up of clamped graphite components); U.S. Pat. No. 5, 191,924, Mar. 9, 1993 (built-up ingot mold having a large pair and a small pair of cooled plates with comer fittings); U.S. Pat. No. 5,318,098, Jun. 7, 1994 (graphite ring casting mold); U.S. Pat. No. 5,323,841, Jun. 28, 1994 (annular casting mold frame supported below, rather then above, a graphite casting mold made up of clamped components); and U.S. Pat. No. 5,518,063, May 21, 1996 and U.S. Pat. No. 5,685,359, Nov. 11, 1997) (continuous casting apparatus having graphite casting ring and use of liquid that cools the mold to directly cool the cast metal).
In addition, U.S. Pat. No. 5,678,623, Oct. 21, 1997, to Steen, et. al., which discloses a permeable unitary graphite casting ring, is incorporated herein by reference.
While the foregoing are considered to accurately represent the state of the art, there are many other patents and many publications that bear upon the subject.
The difficulties in making large graphite casting rings has been described and some solutions have been proposed, for example, in U.S. Pat. No. 4,947,925, which describes the graphite casting annulus made by clamping graphite side pieces and end pieces together. The term “annulus” is used herein generally in the same sense as that term is used in said U.S. Pat. No. 4,947,925, i.e. to mean an enclosed space, which may or may not be circular, surrounded by graphite. U.S. Pat. No. 5,323,841 discloses a similarly constructed annular casting annulus made up of clamped components.
Graphite casting annulus structures have, in the past, generally been round and generally been made of a unitary piece of graphite. The practice, still in wide use has many obvious advantages.
It is, however, difficult to make a large unitary casting annulus of a non-circular nature with machining, heating and forming equipment commonly available in the machine shop of a metal foundry or metal casting machine manufacturer.
Wagstaff, et. al., inter alia, proposed making a graphite casting annulus out of a plurality of graphite components, e.g., a pair of sides and a pair of ends. Since the entire graphite annulus must be liquid tight, i.e., there must be no space in the casting annulus into which the molten metal can flow, it is of the greatest importance that the graphite components be positioned closely in contact with each other. In the type of casting apparatus contemplated by Wagstaff, et. al., the graphite casting ring components are captured between upper and lower frame members to provide mechanical support and assure the positioning of the components. It was previously known to use the “barrel hoop” concept of placing the components of the annulus in upper and lower frames and then clamping the components using a clamping band or other structure—as, in principle, has been the practice for centuries in the manufacture of steel banded wooden barrels.
This approach is not satisfactory in the manufacture of other than circular molten metal graphite casting structures because the clamping force is not uniformly applied and because graphite is quite brittle with virtually no resilience. Thus, Wagstaff, et. al., employed special clamping structures and methods in which the components were clamped before being positioned between the upper and lower frame members. Obviously, all of the graphite components must be in place and undamaged before any of them can be clamped. The Wagstaff, et. al, pre-clamping concept is an improvement that helps make the manufacture of larger sized graphite casting annulus molds; however, this concept also introduces complications in assembly, as referred to, and in repair wherein the entire annulus must be re-built to make a minor repair. Additionally, for rectangular ingot making, the size of the annulus can be very large, requiring intricate machining on a very large piece of graphite. Also, specific convex profiles have to be provided in the annulus wall contour and as such manufacture of the mold by the clamping method using large graphite pieces is highly time consuming and expensive from material and labor point of view.
The present invention permits the manufacture of large and varied shape graphite annulus casting molds from a multiplicity of graphite casting annulus insert components that are individually positionable and fixed individually in position without need for clamping.
SUMMARY OF THE INVENTION
The present invention is embodied in apparatus and methods for foundry operations that substantially reduce the raw material costs, machining time, annulus mold fabrication and assembly time, and thereby assembly costs, and mold maintenance and repair costs, leading to an overall substantial reduction in the cost of tooling and ultimately in the cost of foundering the metal.
The invention also provides a low cost alternative for building proto-type tooling required for forming ingots of different shapes and sizes, thereby increasing the flexibility of the foundry operation to quickly adapt to new and complicated sizes and cast product contours. The invention also provides a savings in tooling, spares, consumables and inventory costs.
The present invention may be described, in one facet, as an improved molten metal casting annulus that comprises, in combination, an insert support and cooling frame configured and constructed to define an enclosed planar annular space and defaming an annular face that faces said annular space that is generally perpendicular to the plane of said annular space and a very large number multiplicity of graphite casting annulus insert components (where the number of graphite components would be more than 200 for 100 inches perimeter of metal casting annulus) supported entirely without clamping on said insert support and cooling frame. In a preferred form of the invention, the frame defines one or more annular grooves adjacent said annular face. The insert components are fitted edge to edge on the annular face to define a molten metal casting annulus. The insert components, in a preferred embodiment, defined a lip which is snugly fitted in an annular groove in the support and cooling frame for positioning and locking said insert components in therein. In a preferred embodiment of the invention, the casting apparatus is designed to provide, in addition to the graphite annulus, a lubricating oil and an additional fluid medium selected from the group consisting of a highly
Lin Kuang Y.
Stetina Brunda Garred & Brucker
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