Feeding a mold for continuous casting of metal

The utilization of a feeder immersion type pipe for continuous casting is avoided through an antechamber-like feeder vessel on top of the mold for continuous casting, having a short extension that reaches into the mold cavity and defines a step towards the wall proper from which steel flows in widening cross section to directly form the casting strand. Casting extraction is enhanced by feeding appropriate material, either fluid or a foil, into the space of the mold cavity immediately underneath this step.

BACKGROUND OF THE INVENTION 
The present invention relates to a mold for continuous casting of metal, 
particularly steel, under inclusion of a cooling arrangement, and using a 
separate uncooled supplemental part which is fastened to the charge end or 
inlet of the mold. 
Molds with particular uncooled charge and inlet structure are know, and 
they provide for the flow control of the molten metal into the mold 
without losing any heat, at least not to any significant extent. The 
supplemental inlet or charge part of course has to be of sufficient 
thermal insulation, i.e., it must provide in fact a barrier against heat 
loss from the molten material in order to obtain a pouring flow into the 
mold at a particular casting temperature so that precipitation, bubbles, 
cavities, or the like will not be produced. 
Another purpose of such a supplemental charge element is the replacement of 
so-called injection or immersion tubes or pipes. The supplemental charge 
element is made of ceramic. graphite, or a suitable blend of high 
temperature resistant material. The utilization of a charge tube or 
immersion pipe in a mold for continuous casting does permit a reoxidation 
of the molten material, particularly as far as the metal is concerned as 
it flows through the pipe. On the other hand, these immersion type casting 
pipes or tubes are subject to a natural wear which is significant. 
Moreover, they cause certain precipitation of clay substances in the 
molten material so that in fact certain remnants so to speak of the 
casting pipe can be found in the continuous casting and ingot. This of 
course reduces the quality of the cast metal, which is particularly 
noticeable and detrimental in case of steel. Therefore, in order to avoid 
such inclusions, and to ensure a high quality casting texture, one needs 
several supplemental features in order to make immersion casting pipes and 
injection tubes for charging a mold feasible; the supplemental features of 
course have a cost increasing factor as far as the making of the steel 
product is concerned. 
A particular problem concerning durability of casting pipes, charge 
nozzles, or the like, particularly when they have their ends immersed in 
the molten steel bath, will occur when casting ingots of fairly thin 
dimensions, i.e., a casting having a thickness of less than 100 mm. These 
problems increase with width of the casting. 
German printed patent application No. 2,056,532 discloses charging a mold 
for continuous casting under avoiding of a casting pipe using instead a 
funnel-shaped additive being coupled to the mold through a fireproof 
coupler, such that the casting area of the coupler is in fact a 
continuation of the interior of the mold proper. The opening of the 
fireproof coupler is provided with an enlargement as an entrance which 
matches the funnel-shaped feeder supplement. The mold with attachments, 
coupler, etc., oscillates during casting, but still it was found that this 
configuration in some form impedes the cooling of the cast material, the 
formation of a skin, and separation of the casting as it emerges from the 
mold. 
In accordance with another proposal disclosed in German printed patent 
application No. 1,458,121, corresponding to U.S. patent application Ser. 
No. 286,349, filed June 7, 1963, in the name of George Robert Gardner, the 
entrance of the mold for continuous casting is enlarged and an annular 
insert is tensioned against the front face of the mold. This way one 
obtains inherently an extension of the insert in radial inner direction, 
i.e., one obtains a kind of rim above the upper edge of the mold's cavity. 
The immersion and feeder pipe for this machine ends in the area of that 
annular insert. This kind of configuration favors indeed flow of the metal 
from the precooled section established by this annular insert, the flow to 
occur particularly along the inner wall of the mold proper and the cooling 
portion thereof. Nevertheless it was found that favorable cooling 
conditions are not established in such a manner, but they are required 
particularly for casting of steel. In this sense then this particular 
suggestion lacks a separation zone for that portion of the casting which 
has already a somewhat solidified and strengthened skin. Since adequate 
separation is not ensured, certain inhomogenities in the texture of the 
casting become more or less unavoidable. 
DESCRIPTION OF THE INVENTION 
It is an object of the present invention to improve cooling, and 
particularly cooling conditions in the entrance area of a mold for 
continuous casting under utilization of an uncooled feeder portion to be 
used as supplement whereby particularly requirements inherent in 
continuous casting are met in such a manner that thin and very wide cast 
ingots, i.e., flat slab ingots, can indeed be met. 
In accordance with the preferred embodiment of the present invention it is 
suggested to provide a supplemental feeder and charge vessel to be placed 
on top of a mold for continuous casting such that an extension reaches to 
some extent into the casting opening of the mold, and in the lower end it 
provides a peripheral step in relation to the mold wall. The section of 
the supplemental part reaching into the mold for continuous casting runs 
in fact the molten metal directly towards the cooled mold wall, whereby 
not only a flow separation edge is provided, but also a defined zone of 
cooling in which the casting forms a skin, which will separate from the 
mold wall somewhat downstream. This step portion of the insert may be 
provided with several steps in outward direction to obtain a more 
continuous transition from insert to mold wall. On the other hand, a 
separate immersion type feeder pipe is obviated. The inventive added-on 
part is therefore quite suitable for thin casting cross sections, or for 
thin and wide type cross sections, even if the part begins to wear. 
In addition, it is suggested that in the range of the steps, certain 
supplemental material (fluid) can be provided to enhance the extraction of 
the casting. Such enhancement material will also improve the conditions 
under which the casting separates from the wall. Moreover, these additives 
may even protect the casting against reoxidation. In furtherance of the 
invention, it is therefore suggested to provide through the wall of the 
supplemental element, or through the mold wall itself, or both, 
pressurized lubricants such as inert gases, carbon, casting powder, flux, 
or the like. Herein it is of advantage to provide feeder pipes for these 
casting enhancing materials which will reach the interior in the interface 
between the step and the mold. This particular location is favored from 
the point of view of radial as well as axial geometry, so that indeed the 
additive will lodge between the casting and mold wall. 
The separation of the casting under protection against reoxidation and 
support of this thin skin will also obtain if the extraction enhancing 
material is, for example, a foil which is continuously fed between the 
feeder element at the mold wall. This foil may either be aluminum or a 
steel strip. Providing the foil with a nickel cover enhances the surface 
thereof. The foil may be of a multi-ply configuration having a layer 
facing the mold wall which is provided for lubrication while the layer 
facing the casting has certain adhesive properties. It may be of advantage 
moreover to provide such foil feeding separately on each of the mold walls 
.

Proceeding now to the detailed description of the drawings, FIG. 1 
illustrates a tundish or casting ladle 2 or the like, holding a pool or 
bath of molten metal such as steel 1. The vessel 2 is of relatively thick 
wall construction and is made of refractory material, or at least with a 
refractory lining. A charging stream 3 pours from the bottom opening of 
the vessel 2, there being a plug or stopper 2a provided by means of which 
this opening can be closed. The stream of molten metals 3 pours into 
supplemental feeder vessel or container 4 constructed in accordance with 
the preferred embodiment of the present invention, and being, so to speak, 
an antechamber or feeding vessel for a mold 5 for continuous casting of a 
casting strand, casting, or ingot 7. The two elements 4 and 5 are 
physically firmly interconnected, and they oscillate together as a unit. 
Oscillating a mold is usual procedure, and details thereof are not shown. 
The mold 5 is as such constructed in a conventional fashion, and is 
provided in its interior portion as far as the mold walls are concerned, 
with facilities for cooling of the mold with water or other cooling 
medium. These cooling ducts 10 are schematically shown in FIG. 2. On the 
other hand, the feeder vessel 4 is not cooled and made of fireproof or 
refractory material. 
The feeder vessel 4 has in its bottom portion an extension 4a of tubular 
configuration, and reaches into the opening 5a of the mold. The lower end 
of this extension 4a is a annular surface providing in fact a step 4c from 
the interior of the extension 4a to the correspondingly recessed receded 
mold walls 5b and 5c. The metal pours from the vessel 4 continously 
through the extension 4a, and the reference numeral 7b denotes the outer 
contour of that stream as it pours into the mold cavity in a curved 
configuration directly underneath the step 4c of extension 4a; the curved 
surface portion of this stream is obtained on account of the step 4c 
defined by the end of the extension 4a. The casting stream 7 reaches the 
mold wall in a zone 7c, from which it separates again to some extent as a 
solidifying or solidified skin 7a forms. Reference numeral 7d refers 
basically to the still liquidous core of the casting, which is in effect a 
kind of liquidous continuation of the flow of steel through the extension 
4a. 
Between the wall 5b of the mold the step 4c forming lower end of the 
extension 4a of charging vessel 4, and the uppermost curved surface 
portion of the string 7 a void is shown in FIG. 2 to be more or less 
filled with a fluid medium or material 8 which, generally speaking, 
enhances and furthers the extraction of the casting 7 from the mold. The 
material may be fed to this particular zone through appropriate tubing, 
such as schematically indicated by reference numeral 9a and 9b running 
through the mold wall and through the wall 4b of the vessel 4. The 
material so fed may be of a powderous nature, in which case pressure is to 
be applied to cause the powder to flow through these tubes 9a and 9b. A 
certain pressure is also needed in case this material is an inert gas. 
As shown in FIG. 3, in lieu of powder or a gas a foil 11 is fed through a 
gap between the wall 4b of the vessel 4, including particularly the outer 
wall of the extension 4a and the adjacent surface portions of the mold 5. 
A spool 12 is shown schematically for feeding this foil 11. The foil 
therefore will be fed along the upper portion of the mold wall 5b until 
reaching the step 4c. 
This foil 11 may either be made of aluminum, or it may be a steel strip, 
and it may be provided with a nickel coating. In fact it was found that 
depending upon the surface properties of the foil 11, it may be possible 
to reduce the mold oscillation, i.e., the up and down vibration of the 
casting and equipment, or one may even dispense with this oscillation 
entirely, and can therefore save a considerable amount of equipment. In 
furtherance of this objective, the foil 11 should be provided with several 
layers in a multi-ply fashion, whereby particularly that surface layer of 
the foil 11 which slides along the mold wall 5b will may be made of Nickel 
and will have lubricating property, while the opposite surface layer 
facing the casting is made, so as to be provided with properties that 
enhances adhesion. The down-moving casting carries the foil along, thereby 
providing a kind of self-feeding action. Separate foils should be provided 
for each side of the more or less quadrilateral mold as far as its cross 
section is concerned. Four mold walls 5b, 5c, 5d and 5e are shown in FIG. 
5. 
FIGS. 4 and 5 illustrate a casting machine being composed essentially 
similar to the one shown in FIG. 1 except that there is a double mold 
provided for the continuous casting simultaneously of two strings 16 and 
17. The principle involved, and the construction proposed here, can be 
extended to cover even more than two parallel running casting operations. 
The mold cavity 6 of FIG. 5 is in effect divided by a partition 15 to 
establish in this case two casting chambers 13 and 14, so that 
correspondingly the narrow casting strings 16 and 17 are produced. The 
particular extension of 4a of the feeder vessel 4 is likewise partitioned 
by an adapting part 18 which forms analogous steps 4e and 4f and matches 
the partition 15 of the mold. Partition 18 covers in fact the upper part 
of partition 15 and constitutes also an uncooled portion of this 
antechamber and feeder vessel 4. Here, as earlier, of course the lack of 
cooling of the vessel 4 is necessary in order to avoid premature formation 
of any skin already inside that feeder vessel. 
It can readily be seen that the configuration shown in FIGS. 4 and 5 
permits in fact to cast relatively thin and less wide casting strings, as 
compared with a single strand casting machine, and in this case one can 
indeed dispense completely with any immersion feeder pipe, or the like. 
The feeder chamber as constructed in accordance with the invention does 
not only permit casting of very thin and wide cross-sectional formats and 
contours of steel, but one can readily change a single strand casting ino 
a multiple strand casting machine simply through partitioning of what is 
originally a single mold into plural molds. The casting vessel as such 
remains the same, particularly the feeder chamber requires merely the 
adding of parts such as 15 and 18 in FIGS. 4 and 5. 
The invention is not limited to the embodiments described above, but all 
changes and modifications thereof not constituting departures from the 
spirit and scope of the invention are intended to be included.