Note: Descriptions are shown in the official language in which they were submitted.
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METHOD OF PRODUCING INGOT MOLD STOOLS
The present invention relates to a method of
producing ingot mold stools.
Ingot molds used in the production of steel ingots
usually consist of upright cast iron, box-like shells open
at both ends. To close the bottom for casting steel
therein, the mold is placed upright on a thick cast iron
m~l~~s~boI~` Hence, an ingot mold cavity is formed by the
mold stool on the bottom and the interiOr side-walls of
the ingot mold thereover. A reasonabl~ close fit between
the mold and stool should be assured to prevent leakaye
of molten steel therebetween.
Ingot molds and mold stools-are usually manufac-
tured in accordance with established sand-mold foundry
1~ techniques. While molding techniques for the manufacture
of ingot molds has undergone some refinements, such as chill
casting procedures, mold stools are still usually produced
by conventional age-old foundry practices. Speci~ically,
a rectangular molding flask is placed over and clamped to
a rigid mQlding plate to form an open-topped box-like
structure. Molding sand is then spread over the inside
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bottom to a depth of several inches (cms.), and then com-
pacted to form a flat sand surface. A rectangular pattern,
usually made of wood, is then placed on the flat sand sur-
face such that there is several i.nches tcms.) o~ clearance
between the sides of the pattern and the flask walls.
Molding sand is then compacted into that space. The pattern
is then carefully removed to leave a rectangular cavity in
the molding sand. A pouring gate must also be provided
in the molding sand adjacent to the cavity to funnel molten
cast iron to the bottom of the cavity. After the mold stool
has been cast in the cavity and solidified, the cast metal
is removed from the sand mold, the gate broken-of~ and the
surfaces cleaned. Surface cleaning is usually performed
by hand, using a pneumatic chipper to scrape-off the molding
sand adhering to the as-cast surface.
According to the present invention, there is
proviaed a method of producing ingot mold stools having
smooth flat surfacas, comprising the steps of placing a
first flat, thermally insulative board onto a flat, hori-
~ontal heat resistant surface, placing a rigid moldingflask over said first insulative board such that the molding
flask holds said first insulative board in place and pro-
vides a peripheral seal at the interface, lining the inside
surfaces of said molding flask with vertically disposed
thermally insulative boards, casting molten iron into the
cavity defined by the first horizontal insulative board
and the vertica:L insulative boards thereover, allowing said
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cast iron to solidify and removing the iron casting fromthe insulative board mold.
The invention is further described, by way of
example, with reference to the accompanying drawings, in
which:-
Figure 1 is a cross-secitional side view of a
mold used to cast an ingot mold stool according to this
invention,
Figure 2 is a cross-sectional side view of a
gate shown in Figure 1, and
Figure 3 is a partial top view of the mold.
With reference to Figure 1, an ingot stool mold
is formed by first providing a smooth flat surface 10
upon which the rest of the mold is constructed. For
example, a metallic plate 1~ may be laid flat on the foundry
floor. Thereafter, a rectangular thermaily insulative
board 14 is placed on top of surface 10. A rectangular
molding flask 16 is then placed on top of insulative board
14. Insulative board 14 should be suitably sized so that
it extends at least to the outer perimeter of molding
flask 16 so that the weight of flask 16 will readily hold
insulative board 14 in place and provide as much of a seal
therebetween as possible. Foux thermally insulative boards
18 (only two are shown) are then secured to the inside
surfaces of molding flask 16. Although any suitable means
may be used to secure insulative boards 18 to the inside
face of flask 16, it is preferred to use a commercially
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available nailing system wherein a nail is driven through
the molding board 18 and into the molding flask 16 to
hold the insulative boards 18 in place.
Although it is possible to cast the molten iron
directly into the open-topped mold as shown in Figure 1,
it is preferred to provide a gate, as shown in Fi~ure 2,
so that the smooth flat surface of insulative board 14 is
not disturbed. The gate is formed by providing a small
rectangular extension 20 on one wall of flask 16 (Figure 3)
sufficient to receive a preshaped and baked sand gate 22
having a pouring gate 24 therethrough.
When the mold is completed as shown in the
- drawings, molten iron is cast into gate 28 filling the
mold cavity defined by insulative boards 14 and 18, and
the molten metal therein is allowed to solidify. When
- solidified, the casting is removed and the gate metal
broken-off. The resulting casting~ i.e. those surfaces
formed against insulative boards 14 and 18 are exceptio~ally
smooth and flat. Since no sand was used to form any of the
stool surfaces, no chipping or surface conditioning is
necessary. All that may be necessary is that portions o~
the insulative boards may have to be scraped-off.
The procedure as described above not only elimi-
nated the use of molding sand ~except for the gate) but
it also significantly reduces the manpower necessary to
produce the mold and to condition the casting, and it also
produces a cast stool of greatly improved quality. The
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quality improvements are not only physical in that the
surfaces are smoother and flatter as compared to stools
produced in sand molds, but also such stools have been
shown to have a longer average life. For example, the
first mold stool produced accord:ing to the above-described
embodiment was used in excess of 100 pours, whereas prior
art stools are scrapped after about 50 pours on an average.
After the above-described practice was established as the
standard practice for producing mold stools in one foundry,
the stool condemnation rate dropped over a period of eight
months from 18 lbs/ton to 14 lbs/ton (9 kg/tonne to
7 kg/tonne). The condemnation rate is the weight of stool
scrapped per unit weight of steel poured thereon. The
improved rate of 14 lbs/ton (7 kg/tonne) noted above`does
not fully re~lect the advantages of this invention as it
is the rate of all stools on hand including those produced
pursuant to prior art practices. Hence, the improved rate
of from 18 lbs/ton to 14 lbs/ton (9 kg/tonne to 7 kg/tonne)
reflects a gradual improvement in condemnation rate as the
stools produced by this inventive method gradually increase
in number and in proportion to the prior art stools.
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