Metal founding – Means to shape metallic material – Continuous or semicontinuous casting
Reexamination Certificate
1996-05-23
2001-01-16
Ryan, Patrick (Department: 1722)
Metal founding
Means to shape metallic material
Continuous or semicontinuous casting
C164S432000, C164S437000, C222S591000
Reexamination Certificate
active
06173755
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to continuous slab casting of metals, and more particularly to a molten metal delivery nozzle for continuous slab casting which reduces turbulence and premature freezing of the molten metal, thereby improving the surface quality of the resultant casting.
Continuous casting techniques have been used to form slabs or strips of various metals such as aluminum, copper, zinc and steel. Several types of continuous casting machines are known. For example, one type of casting machine comprises an opposing pair of moving continuous belts which form a mold into which molten metal is introduced. U.S. Pat. Nos. 4,602,668, 4,785,873 and 4,798,315 disclose such continuous belt casting machines.
Continuous slab casting machines have also incorporated opposing caterpillar-type molds in place of continuous belts, as shown in U.S. Pat. Nos. 3,774,670, 4,290,477, 4,485,835 and 4,619,309.
Prior art slab casting machines have also incorporated a single flat surface onto which the molten metal is cast. U.S. Pat. No. 4,721,152 discloses one such single-belt continuous casting machine.
A major disadvantage of prior art continuous slab or strip casting machines is the production of castings having poor surface quality due to such factors as molten metal turbulence and premature solidification near the nozzle tip. These problems are thought to result from meniscus instability of the molten metal at the nozzle discharge area. Attempts have been made to reduce meniscus instability by methods such as shrouding the molten metal with inert gas as it exits the nozzle. However, the control of meniscus instability by such methods is difficult and has not resulted in a consistent production of castings having optimum surface quality.
The present invention has been developed in view of the foregoing and to overcome other deficiencies of the prior art.
SUMMARY OF THE INVENTION
The present invention provides an improved molten delivery nozzle for continuous slab or strip casting which reduces turbulence, backflow and premature freezing of the molten metal, thereby producing cast slabs having highly superior surface quality. The improved nozzle promotes meniscus stability during the casting operation which reduces porosity and improves the surface quality of the cast products.
An object of the present invention is to provide an improved molten delivery nozzle for use in slab or strip casters.
Another object of the present invention is to provide an apparatus for casting a metal slab or strip including a casting mold and a molten delivery nozzle slidingly engaged with the casting mold for delivering molten metal to the mold. The nozzle includes at least one resilient, thermal insulation layer which provides a seal between the casting mold and nozzle, and prevents premature solidification of molten metal near the nozzle tip. The casting mold may comprise a continuous belt or caterpillar mold, or may comprise a stationary mold.
Another object of the present invention is to provide a molten metal delivery nozzle having a sloped configuration which reduces molten metal turbulence during the casting operation.
Another object of the present invention is to provide a method of casting a metal slab or strip including the use of a casting mold and a molten metal delivery nozzle in sliding engagement with the mold. Molten metal is delivered through the nozzle into the mold where it solidifies to form a slab or strip. During the casting process, the meniscus of the molten metal is controlled in order to improve surface quality of the resultant slab. The nozzle is configured such that it reduces turbulence, backflow and premature solidification of the molten metal at the nozzle tip. The method may include the use of horizontal or vertical continuous casting machines.
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Clements Donald J.
Fang Que-Tsang
Li Nai-Yi
Aluminum Company of America
Lin I.-H.
Ryan Patrick
Topolosky Gary P.
Towner Alan G.
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