Process and apparatus for vertical continuous casting of metal

Process and apparatus for vertical continuous casting of metal in at lest one hot-top mold with metal supplied at constant level. The object of the invention is to provide a process and an apparatus that make it possible, while supplying metal at constant level, to avoid non-uniform temperature gradients, turbulence, and waste of metal. According to the invention this is achieved by coordinating the level, flow rate and distribution of molten metal to each hot-top mold from the outlet opening of a smelting furnace. This is produced by a pouring spout or trough that is supported through the upper wall area of each hot-top mold to supply molten metal to each hot-top mold through central outlet openings in the side walls of the trough, with the bottom of the trough being in a plane below the level of the outlet opening of the smelting furnace and below the upper surface of the melt in the hot-top mold, and with the trough outlet openings supplying molten metal to the center of each mold and causing it to flow outwardly therefrom.

BACKGROUND OF THE INVENTION 
The invention relates to a process and an apparatus for the vertical 
continuous casting of metal in one or more hot-top ingot molds with metal 
supplied at constant, uniform level to each said mold. 
DISCUSSION OF THE PRIOR ART 
Supplying metal at constant level to hot-top ingot molds is known. In the 
"Aluminium-Taschenbuch" [Aluminum Handbook] (14th edition, 1984, p. 23), a 
so-called hot-top casting method is described in which feeding of the 
molten metal, such as aluminum, is not done in tile usual manner, through 
a nozzle-float system which, after the level of the melt in the mold 
sinks, allows more molten metal to flow through the metal casting which 
has hardened and moved vertically downward. In the described method, a 
constant level of the molten metal is maintained by the arrangement of the 
molds and the molten metal supply lines on a single plane. According to 
the principle of communicating tubes, the level of the melt can be kept 
constant all the way back to the smelting furnace. Because of the vertical 
downward movement of the hardened metal in the hot-top mold, the liquid 
metal is supplied through simple lateral feed from openings in the side 
wall of the metal supply trough, spillway or spout located next to the 
molds and through openings in a side wall of the molds, to the continuous 
casting. In this manner, four or more molds can be supplied simultaneously 
with molten metal. The process described in the aforementioned 
publication, and the corresponding apparatus, have a variety of 
disadvantages. The unilateral asymmetric supply of molten metal can result 
in turbulence or splattering, especially at start-up. In addition, the 
creation of temperature gradients between the feed spout discharge 
openings and the opposite wall of the mold cannot be avoided, so that the 
hardening behavior of the metal is uneven and non-uniform. Another 
disadvantage is the volume of the residue of metal that remains in the 
feed spout or trough and does not flow through the side wall, which volume 
can not be supplied to the mold, especially toward the end of the pouring 
process. 
Therefore there is a need for a method and an apparatus which make it 
possible to avoid asymmetric temperature gradients, turbulence, and wasted 
volumes of metal while supplying molten metal, such as aluminum, to a 
vertical continuous casting at the same level as at the smelting furnace 
outlet. 
SUMMARY OF THE INVENTION 
According to the present invention, equality of the levels of a molten 
metal in each hot-top ingot mold and at the outlet opening of a smelting 
furnace is produced by means of a trough, spillway or pouring spout that 
is guided through the upper part of the hot-top ingot mold and which 
provides a communication with the molten metal in the hot-top ingot mold 
through discharge openings in the side walls of the trough, with the 
bottom or floor of the trough being on a plane below the level of the 
metal at the outlet opening of the smelting furnace and below the upper 
level of the molten in the hot-top mold. 
The trough, spillway or pouring spout may be associated with a plurality of 
hot-top molds located on the same plane. The flow of molten metal from the 
trough is promoted by the vertical downward movement of the hardened 
molded continuous metal body being formed in each hot-top mold. 
The apparatus; according to the invention is characterized by the fact that 
the trough, spillway or pouring spout, which conveys a continuous stream 
of metal into the open top of each hot-top ingot mold is supported into 
and out of each intermediate mold through opposed openings in an 
insulating collar that forms a surrounding wall around the upper part of 
each hot-top ingot mold, so that the bottom of the trough or pouring spout 
is just below the surface level of the melt confined within the mold by 
the insulating collar of the hot-top mold, and by the fact that within the 
walled area formed by the insulating collar, the side walls of the trough 
or pouring spout have opposed outlet openings to allow the molten metal 
stream to spill out into a central area of the melt and to flow towards 
the opposed walls of the mold for uniform circulation. 
On the basis: of the direct symmetric guidance and support of the trough, 
spillway or pouring spout, and the central opposed outlet openings for the 
passage of the stream of metal, a maximally laminar flow pattern is 
produced in the mold. This arrangement makes it possible to distribute or 
circulate the stream of metal from the middle of the surface of the molten 
metal in each ingot mold uniformly to the outer periphery or circumference 
of each mold. The solidifying surface of the metal body being formed are 
subjected to uniform supply, and a fine grained and especially uniform 
metal structure is produced. This results in a defect-free surface area of 
the molded metal body, so that the previously-required step of milling 
prior to further processing can be limited to a much smaller surface area 
of the cast metal body. No undesirable non-uniform temperature gradients 
occur, so that symmetric hardening occurs. At the end of the pouring 
process, the entire metal melt flows practically quantitatively into the 
molds. 
The trough, spillway or pouring spout can be connected with a plurality of 
hot-top molds. It communicates with the smelting furnace to convey the 
molten metal, such as aluminum, to each of the molds. 
Since the pouring spout or trough, with its outlet openings, is surrounded 
on all sides by molten aluminum metal, within the insulating collar inside 
the mold, it should preferably be made of one-piece ceramic material. When 
there are several molds supplied by the same trough, the ceramic 
components should be aligned and interconnected through the intermediate 
molds. To cut off the metal stream at the terminal mold, a ceramic sealing 
element is provided at the end of the trough. The latter consists of a 
sealing wall, preferably made of ceramic material, and of the same height 
as the surrounding side walls of the trough. If an extension of the trough 
should become necessary later on, the sealing element can be removed as 
desired and fastened to the new end of the extended trough. 
An embodiment of the invention is described in detail with reference to the 
accompanying drawing.

DETAILED DESCRIPTION 
The hot-top ingot mold shown in FIG. 1 has a rectangular cross section and 
consists of the mold frame 4 provided with cooling channels 6 and an upper 
insulating collar 2 forming a surrounding wall. A hot-top strip 3 is 
mounted on a support surface 7 surrounding mold frame 4, on which strip 
the insulating collar 2 rests. Insulating collar 2 consists of a loading 
chamber 13 provided with an insulating covering. Insulating collar 2 
surrounds and confines the ingot mold at the top, and the opposed long 
walls thereof are intersected at central areas by a pouring spout or 
trough. The side walls 8 of the trough are flush with the upper sealing 
edge 9 of the insulating collar 2. The trough or pouring spout 1 has 
opposed discharge openings 10 located symmetrically at central areas of 
its two side walls 8, said openings serving to permit the melt to flow 
into the center of the mold. The stream of metal 5, which comes from a 
smelting furnace (not shown here), is guided through the discharge 
openings 10 into the middle of each ingot mold. Extension 11 of trough 1 
leads to the next ingot mold. During the continuous casting process, the 
level of the metal in trough 1 and in loading chamber 13 of the mold is 
the same. The gravity flow of metal stream 5 is produced by the vertical 
downward movement of the hardened ingots being formed in each ingot mold. 
In FIG. 2, the hot-top ingot mold is shown filled with molten metal. It is 
evident that only one metal level exits in the entire casting system. The 
level of the metal in pouring spout, spillway or trough 1 and insulating 
collar 2 extends to just below the upper edge of trough 1 and/or collar 2. 
To regulate the level of the metal, a simple level sensor 14 can be used 
in all molds. This controls in known fashion the tilting movement of the 
smelting furnace and the flow rate when pouring the molten metal into 
spout or trough 1. FIG. 2 also shows the flow pattern achieved according 
to the invention. The main flow 5 through the transverse openings 10 is 
directed towards the far-distant narrow sides of the rectangular mold and 
produces a uniform circulation over the solidifying surface of the metal 
block being produced. A flow that is as uniform as possible over the 
solidifying surface, especially in the areas that are very important for 
the quality of the casting, in the outer edges of the molded metal body 
being created, is of critical importance to the optimization of the 
vertical continuous casting process. So-called cold spots can also be 
reliably avoided in the corner areas of the mold, so that the surface 
quality of the finished metal block is much smoother and more uniform than 
in previous methods with interrupted metal supply. 
It should be understood that the foregoing description is only illustrative 
of the invention. Various alternatives and modifications can be devised by 
those skilled in the art without departing from the invention. 
Accordingly, the present invention is intended to embrace all such 
alternatives, modifications and variances which fall within the scope of 
the appended claims.