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Патент USA US3039167

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June 19, 1962
J. w. MUELLER
3,039,158
HIGHLY THERMALLY EFFICIENT HOT TOP AND PREFORMED PROTECTIVE
REFRACTORY AND EXOTHERMIC UNIT THEREFOR
Filed Sept. 22, 1960
2? .24]
r42
INVENTOR.
JW-IA/ W Ml/EZLER
BYM
,4rromvsys
ilnited gtates
3,039,158
Patented June 19, 1962'
1
2
3,039,158
from the high quality hard dense ?rebrick by being rather
porous, fragile, of poor mechanical strength, but having
HIGHLY THERE/[ALLY EFFECIENT HOT TOP AND
good heat insulating properties and low heat’ absorption
PREFGRMED PRQTEQTI‘VE REFRACTORY AND
EXOTIERMIC UNIT THEREFQR
characteristics. However, these insulating ?rebrick lin
ings, unless protected, are quickly destroyed by the heat
John W. Muelier, Rocky River, ()hio, assignor to Oglehay
Norton Company, Cleveiand, Ohio, a corporation of
Delaware
Filed Sept. 22, 1960, Ser. No. 57,782
4 Claims. (Cl. 22—147)
This invention relates to a hot top and particularly to
a highly thermally e?icient hot top.
As is Well understood in the art, hot tops are used'
4t'im!e’
nice
of the molten metal which usually is 2800° F. to 2950°
F., that is, the insulating ?rebrick linings by themselves
do not constitute semipermanent linings capable of being
used for a substantial number of pouring operations be
fore being replaced. These commercial insulating ?re
brick linings have temperature resisting use ratings of
from 1600” F. to 2600° F. which are less than the tem
perature of the molten metal in the hot tops. In order
in conjunction with ingot molds in the casting of metal
to make the insulating ?rebrick linings semipermanent
ingots such as steel ingots. The purpose of the hot tops
is to provide a reservoir of molten metal therein which
feeds the pipe or shrinkage cavity as it tends to form in
the solidifying ingot in the mold and thus enable the
production of solid ingots which can be further processed
ones capable of repeated use, they have been covered with
a protective refractory veneer applied to the inner surf-ace
of the linings and dried in situ, or have been covered by
preformed refractory inserts inserted into the hot tops.
The protective veneers or inserts are onlysingle use expedi
without necessitating expensive scrapping of metal. In
order that the hot tops perform their function e?iciently
veneers or inserts need only be sufficiently thick to provide
ents and are replaced for each pouring operation. These
the required temperature drop or gradient between the
temperature of the molten metal and the rated use tem
perature of the insulating ?rebrick linings. As an exam
and remains in a ?owable molten condition to feed the 25 ple, if the rated use temperature of the insulating ?rebrick
and economically it is a requisite that the hot tops be
thermally e?icien-t so that the molten metal therein does
not solidify as quickly as the molten metal in the mold
pipe or shrinkage cavity forming in the solidifying ingots.
Although single use or all refractory hot tops are
lining is 2600° F., then the temperature drop needed
would only be 200° F. to 350° F.
It has been found
employed to some extent, substantial numbers of com
that hot tops provided with insulating ?rebrick linings and
posite hot tops are used. These composite hot tops have
metal casings which are provided with refractory linings.
the protective veneers or inserts have substantial increased
The composite hot tops can be reused for a number of
thermal efficiency since the insulating ?rebrick linings pre
vent heat losses due to their good heat insulating proper
pouring operations although, as is known in the art, they
ties while the protective refractory veneers or inserts are
require a measure of preparation for each pouring op
not su?iciently thick to cause high heat absorption therein
from the molten metal in the hot tops during the time
period the latter function.
eration.
The metal casings of the composite hot tops have been
lined heretofore with hard dense high quality ?rebrick
The hot tops having the insulating ?rebrick linings pro
tected by the veneers or inserts require a relatively low
volume of metal therein and since the heat losses from the
metal are reduced the metal remains molten and flowable
head of the ingot. These high quality hard dense ?re 40 a su?icient length of time and functions satisfactorily to
feed the pipes or shrinkage cavities in the solidifying in
brick linings are semipermanent linings in that they can
gots. It has been found that these more thermally e?i
be used for a number of pouring operations. This is
cient hot tops require a volume of metal therein which is
due to the fact that such linings have good mechanical
only 10% to 12% of the total molten metal in the molds
strength and heat resistant characteristics. However, the
high quality hard dense ?rebrick linings, because of their 45 and hot tops. Also, it has been found that these more
linings which, in the use of the hot tops, is covered with
a thin paint-like slurry to ?ll up cracks in the lining and
to facilitate the stripping of the hot tops from the sink
"i
density, do not have good heat insulating characteristics.
Also, these linings due to their density and mass are
highly heat absorbing and absorb so much heat from the
molten metal in the hot tops in the time period that hot
tops function that they produce a chill in this molten
metal causing the same to solidify too quickly and hence
to lessen the e?iciency of their function of feeding the
pipe or shrinkage cavity forming in the solidifying ingots.
In order to compensate for the poor heat insulating
thermally e?icient hot tops produce an increase of 3%
to 5% in sound ingot yields as compared to the sound
ingot yields when using hot tops lined with the high quality
hard dense ?rebrick linings ?rst described above.
The present invention contemplates the provision of hot
tops having a still higher thermal e?iciency such that they
will require a volume of molten metal which is only ap
proximately 7% or less of the total volume of molten
metal in the hot tops and molds and will thereby further
characteristics and the high heat absorption of these 55 increase the sound ingot by an additional 3% or more as
compared to the sound ingot yields of the previously de
high quality hard dense ?rebrick linings, it has been neces
sary to have the hot tops of a size such that they con
tain a volume of molten metal equal to 15% or 16%
of the total and combined volume of molten metal in
scribe-d hot top constructions.
'
The invention further contemplates that this hot top of
increased thermal e?iciency will ‘be so constructed inter
the molds and hot tops even though only 3% to 5% 60 nally as to produce the advantageous results referred to
and at the same time will enable its insulating ?rebrick
of the molten metal in the hot tops is required to feed
lining to be a semipennanent one capable of being reused
the pipes or shrinkage cavities that tend to form in the
for a number of pouring operations, by the use of an
solidifying ingots.
improved protective single use protection which can be
Inasmuch as the sinkheads on the ingots, formed by
the solidi?ed metal remaining in the hot tops, are cropped 65 readily applied to the insulating ?rebrick lining during the
preparation of the hot top for alpouring operation.
later from the ingots and scrapped, it will be realized
More speci?cally the invention contemplates a com
that a ‘substantial loss of metal occurs with substantial
posite hot top which has a semipermanent insulating ?re-'
increase in the cost of ingots.
brick lining covered with 1a preformed, dried, relatively
In an effort to improve the thermal e?iciency of hot
tops to permit the use of lower volumes of metal in the 70 dense, mechanically strong refractory panel insert which
hot tops, the metal casings of composite hot tops have
has applied to and integrated with its exposed surface a
been lined with insulating ?rebrick which are distinguished
facing layer of exothermic material. The protective panel
3,039,158
33
4
inserts are relatively thin so as not to have great heat ob
?rebrick which, because of their density and mass do not
have good heat insulating characteristics and low heat ab
sorption quality, and they provide the desired tempera
sorption property, although they do have good mechani
ture drop or gradient between the temperature of the mol
ten metal and the rated use temperature of the insulating
cal strength. The insulating ?rebrick lining of the hot top
embodying the invention is mounted between and is sup
ported by the ?anges 12 and 13 of the casing. The in
sulating ?rebrick lining in combination with the preformed
panel inserts having a refractory layer and an exothermic
facing layer thereon constitute a novelty of the present
?rebrick linings and, in addition, they protect the latter
from the heat and ?uxing actions of the exothermic lay
ers. The exothermic layers on the relatively thin protec
tive panel inserts avoid chills of the molten metal in the
hot tops due to heat absorption therefrom by the refrac
invention and will be described in greater detail herein
tory panels since said exothermic layers function to re
duce heat absorption by the panel from the molten metal
after.
The hot top illustrated has a downwardly divergent or
in the hot top.
tapered interior although they may also be made with
no taper and in preparing for a pouring operation the
The use of hot tops constructed as contemplated by
the present invention eifects substantial savings and in
creases the e?iciency of ingot production in that the size 15 hot top is placed in a suitable stand in inverted position
as is well understood in the art. The insulating ?rebrick
of the sink-head which is subsequently scrapped is greatl
lining of the hot top casing is semipermanent in that it
reduced thereby substantially increasing the yield of sound
is used for a number of pouring operations. The pre
steel from the ingot.
formed panel inserts 23 and 24 are. inserted into the in
The invention contemplates a preformed relatively
terior of the hot top and placed in correct position in
dense, essentially nonfragile, self-sustaining, mechanically
contact with the insulatinglining 21 ‘and inside of ledge
strong refractory insert that supports a facing layer of
12 as shown, or they may be stopped off and ?t under
the wider ledge 12 as explained above. Then the re
exothermic material and acts as a heat buffer between the
exothermic facing layer and the insulating ?rebrick lining.
fractory bottom ring 14 is placed on the lower end of the
This concept produces a low volume hot top requiring a
minimum amount of exothermic material as the facing 25 hot top as will be well understood. This bottom ring is
provided with a raised rib portion 15 extending upwardly
layer and hence a minimum volume hot top for minimum
past the inner end of ?ange 13 and underlying the in
cost. Hot tops embodying the invention are economically
competitive with other hot tops used for producing in
gots of all grades of steel as distinguished from known
exothermic hot tops which are prohibitive cost-wise ex
sulating ?rebrick lining. The refractory bottom ring 14
is shown as provided on its inner periphery with a re
30 cessed portion 16 furnishing a shoulder that supports the' if
cept for use in connection with production of high grade
high cost alloy and stainless steels.
During the following detailed description of an embodi
ment of the invention further advantages resulting there
from will become apparent such description being taken in
conjunction with the accompanying drawing forming a
part of this speci?cation and wherein:
preformed panel inserts. It will be understood that/the
rib 15 might be wider and the recessed portion 16 (,m'iitted
and the panel inserts then would engage the upper‘surface
of the wider rib- 15 of the bottom ring. The usual wiper
strip 17 may be positioned between the lower end of the
‘casing and the upper side of the bottom ring as is well un
derstood in the art. Also any space or clearance between
the bottom ring, the metal casing and the lower end of
FIG. 1 is a view partly in elevation and partly in sec
the insulating ?rebrick lining can be sealed with a suitable
tion of a hot top of the composite ?oating type con
structed in accordance with the present invention and 40 sealing compound as indicated at 18. The refractory bot
tom ring 14 and the wiper strip 17 are secured to the
shown mounted in the open upper end of an ingot mold,
casing in the usual way by suitable attaching clips (not
a portion of the latter being illustrated in section.
FIG. 2 is an elevational view of the preformed panel
shown) as is well understood in the art.
When the hot top thus equipped is used for a pouring
insert having a refractory layer and an exothermic facing
operation, it is positioned a predetermined distance in the
layer thereon which are used to protect the insulating
upper open end of an ingot mold l9 and initially held in
?rebrick lining for the side walls of the casing.
such position by suitable. blocks such as the wooden blocks
FIG. 3 is a view similar to FIG. 2, but shows the pro
20; After the pouring of the molten metal into the mold
tective panel insert having a refractory layer and an
and the hot top, the blocks 20 are knocked out or de
exothermic facing layer thereon and used to protect the
insulating ?rebrick lining at the corners of the casing of 50 stroyed and thereafter the hot top ?oats on the molten
metal in the ingot mold. The preparation and use of the
the hot top, and
,
hot top as broadly described above is well known in the
FIG. 4 is a sectional view of a portion of the hot top
shown in FIG. 1 and is taken substantially on line 4—~4
art.
The insulating ?rebrick lining is shown as formed of
of FIG. 1 looking in the direction of the arrows.
side portions 21 and corner portions 22. The portions 21
The hot top shown in the drawing insofar as its metal
and 22 have their contacting surfaces shaped to closely
casing and its manner of use are concerned may be said
inter?t one another and to closely interlock in position in
to be conventional. The metal casing of the hot top is
the hot top between the lips or ?anges 12 and 13 of the
illustrated as formed of an upper section 10 and a lower
casing. The insulating ?rebrick lining extends inwardly
section 11 suitably secured together. The hot top‘ is
shown as being of rectangular con?guration, but it will 60 beyond the inner end of the lower lip or ?ange 13 and
overlies the raised rib 15 of the bottom rim 14, as clearly
be understood it might be of round, oval or other con
?guration.
_
shown in FIG. i1.
As previously stated, the insulating ?rebrick lining is
The upper section 110‘ of the metal casing is shown as
rather porous, fragile and of poor mechanical strength
provided at its upper end with an integral inwardly ex
but has good heat insulating properties and low heat
tending lip or ?ange 12, which may extend into the
absorption characteristics. However, insulating ?rebrick
inside face of the insulating brick lining as shown or it
of this type have a rated temperature use of between
may extend into the inside face of the insert. The lower
1600° F. and 2600" F .and since the temperature of the
section or part 11 of the metal casing has at its lower end
molten metal is between 2800" F. and 295G° F., the
an integral inwardly extending lip or flange 13, which is
of less width than the ?ange 12.
70 lining would be destroyed or so severely damaged by the
thermal shock of direct contact with the molten metal it
The metal casing is lined with porous, fragile, insulat
ing ?rebrick 21 of poor mechanical strength but good heat
insulating properties and low heat absorption character
istics. These insulating ?bebrick constituting the lining
are distinguished in this way from high grade, hard, dense 75
would have to be replaced for each pouring operation.
This destruction or damaging of the lining also would be
increased because of the mechanical abuses to which it
would be subjected during the stripping of the hot top
as?»w
3,039,158
.
.
.
5
.
from the sinkhead after the ingot had attained the desired
degree of solidi?cation. Also, at such time the colder
air passing through the stripped hot top and contacting
the then hot insulating ?rebrick lining would subject such
lining to further destructive thermal shock.
Heretofore it has been proposed to protect the insulat
ing ?rebrick lining of a hot- top from thermal shock and
mechanical abuses by. covering said lining with a pro
.
.
.
6
hulls like oats or rice. In addition, the exothermic com
position will contain a suitable heat destructible binder.
The exothermic composition after being thoroughly mixed,
is placed in the panel molds on top of the refractory com
position which may or may not have been previously
dried ‘and then the exothermic composition or the re
fractory composition and the superimposed exothermic
composition are thoroughly dried as, for instance, by be
ing baked at temperatures not high enough to ignite the
tective veneer or a preformed protective panel insert.
The purpose of using the protective veneer or panel in 10 exothermic composition. In either event the refractory
composition and the exothermic composition become at
sert is to provide a su?icient tempertaure drop or gradi- _
tached or integrated together when dried.
ent between the temperature of the molten metal and the
Although the thickness of the refractory layers and of
temperature to which the insulating ?rebrick lining would
be subjected to one within the rated temperature use of
the lining.
-
The present invention contemplates protecting the in
sulating ?rebrick lining of the hot top casing so that it
Will be a semiperrnanent lining capable of being reused
proximately one-quarter to one-half inch thick so that the
integrated layers of the panels will have a total thickness
of approximately one-half inch to one inch.
greatly increasing the thermal e?iciency of the hot top
The refractory supporting layers of the protective panels
provide the required temperature drop or gradient be
enabling a lower volume of metal to be used therein than
tween the temperature of the molten metal and the tem—
for a number of pouring operations and at the same time
“vim-1
the exothermic layers of the preformed protective panels
15 may vary, it is contemplated that each layer will be ap
perature to which the insulated ?rebrick lining is subjected,
is ordinarily the case and thereby improving the yield of
that is, the insulating ?rebrick lining will not be sub
sound steel from the ingot.v
jected to a temperature higher than its rated use tem
The preformed protective inserts for the insulating
?rebrick lining of the hot top in accordance with the in 25 perature. While the refractory supporting layers of the
panels are hard, dense, essentially nonfragile and self
vention comprise a dense, essentially nonfragile, self
sustaining, they do not because of their relative thinness
sustaining refractory supporting layer having integrated
provide sufficient mass to absorb high quantities of heat
therewith on one side an exothermic facing layer. The
from the molten metal such as would be enough tovpro
protective covering for the insulating ?rebrick lining may
be preformed as a single insert unit or they may be pre
formed as separate side panel inserts 23 and corner panel
inserts 24, which have their contacting edge surfaces
shaped to closely inter?t and mutually interlock. The
protective panel inserts 23 and 24 when positioned in the
hot top have their refractory supporting layers 25 and
25a contacting the insulating ?rebrick lining while the exo
thermic facing layers 26 and 26a of the panel inserts 23
and 24 bound the interior of the hot top.
The inner surfaces of the insulating ?rebrick lining may
have a slurry made from sea coal or other suitable ma
terial sprayed or otherwise applied thereto or this slurry
may be applied to the surfaces of the refractory support
ing layers of the panel inserts which contact the lining.
The purpose of the slurry is to prevent penetration of
molten metal onto the insulating brick lining should the
metal accidentally seep through the joints between the
panel insert units and to prevent fusing of the panel in
serts to the insulating ?rebrick lining which would hinder
the stripping of the hot top from the sinkhead.
duce a chill in the molten metal and lessen the ef?ciency
of the hot top. Also the refractory supporting layers of
the preformed panels keep the exothermic facing layers
thereof out of direct contact with the insulating ?rebrick
lining and hence the latter is protected from and is not
directly subjected to heat generated by the exothermic
layers.
The exothermic facing layers 26 and 26a of the pre
formed protective panels 23 and 24 when ignited by the
molten metal during the use of the hot top serve to com
40 pensate for heat losses and heat absorption from the
molten metal and thus to increase the thermal efficiency
of the hot top.
It will be seen that the refractory supporting layers
of the protective panels not only act as a supporting means
for the facing exothermic layers thereof, but provide an
effective heat buffer between the molten metal and the
insulating ?rebrick lining and between the exothermic
facing layers and the insulating ?rebrick lining. The re
fractory supporting layers of the panels also protect the
The refractory supporting layers 25 and 25a of the 50 insulating ?rebrick lining from the ?uxing action produced
by the reaction of the exothermic layers, and thus prolong
preformed protective panel inserts are formed of a high
the life of the insulating ?rebrick lining. The use of the
silica heat resistant composition. This composition may
refractory supporting layers in combination with the exo
vary considerably in its constitutent makeup but a suitable
thermic facing layers of the protective panels and with
one has been found to consist in ?ve to eight parts by
weight of silica sand to which is added one part by weight 55 said panels covering the insulating ?rebrick lining make
it possible to produce an extremely low volume hot top
of liquid sodium silicate of approximately 40° Baumé
while utilizing a minimum amount of exothermic mate
speci?c gravity. These materials are thoroughly mixed
rial, thus providing such a low volume hot top at a mini
and the composition is placed in molds and formed to the
mum cost. A hot top construction in accordance with
desired shapes after which the panel is removed from
the mold and dried either before or after the exothermic 60 the invention need only contain a volume of molten metal
which is approximately 7% of the total volume of the
facing layer is molded thereon depending on the materials
molten metal in the hot top and mold and hence even
being used.
though a hot top embodying the invention may be some
The exothermic facing layers 26 and 26a of the panel
what more expensive than other types of hot tops, it is
inserts 23 and 24 may vary in their composition and while
economically competitive with the latter, particularly in
not wishing to be limited to particular exothermic com
connection with the production of lower carbon and non
positions, a number of suitable ones will be referred to.
alloy grades of steel. There are in use hot tops including
The exothermic composition may include sources of car
exothermic agents in their construction but such hot tops
bon, such as coal, coke breeze, tar and graphite; sources
have not been economically competitive or practical ex
of silicon such as ferrosilicon; sources of aluminum such
as dross, or any other materials which, when suitably com 70 cept possibly for high grade, high cost alloys and stain
less steels.
pacted, will in the presence of entrained air or oxygen or
The protective panel inserts being preformed can be
oxygen obtained from an included oxidizing agent, oxi
produced accurately and uniformly as to size and com
dize or burn with the liberation of heat. Also various
position in a plant properly equipped for such produc
farm or forest products or bi-products which will func
tion exothermically may be used such as straw, vegetable
tion. Also the protective panel inserts being self-sustain
5%
contacting said lining, said layer having a lower end por
tion overlapping the inner side of said second portion of
said ring, said lower end portion of said layer and said
ing and essentially nonfragile can be handled, shipped,
stored and used with a minimum of breakage. In addi—
tion, the preformed protective panel inserts facilitate the
preparation of the hot tops for a pouring operation, as
second portion of said ring having interengaging and
compared to applying protective veneer compositions and
exothermic compositions to the brick lining of the hot
inter?tting surfaces acting to support said unit in the hot
top and to seal against metal ?owing between the bottom
ring and said unit.
2. A highly thermally e?icient low volume hot top as
de?ned in claim 1 wherein said interengaging and inter
tops by troweling or otherwise applying the same thereto
and the-n drying such compositions in situ.
Furthermore the preformed protective panel inserts
are thoroughly dried prior to their insertion into the hot 10 ?tting surfaces include a shouldered recess formed in one
of said portions and inter?tting with the other of said
tops and hence the danger is obviated of pouring molten
metal into the hot tops when the protective coverings of
- portions.
3. A highly thermally efficient low volume hot top as
the brick linings are not completely dried.
de?ned in claim 1 and wherein said interengaging and
Although a speci?c structural embodiment of the in
vention has been illustrated and described and certain 15 inter?tting surfaces include a shouldered recess on the
inner periphery of said ring and in which inter'?ts said
refractory and exothermic compositions referred to, it
lower end portion of said layer.
will be understood that the invention is not to be limited
4. A highly thermally efficient low volume hot top as
thereto but is to be construed as including such variations
de?ned in claim 1 wherein said layer of said unit is a
as come within the scope of the appended claims.
Having thus described my invention, I claim:
20 supporting and heat buffer layer and a facing layer of
exothermic material is integrated with said ?rst layer over
1. A highly thermally ef?cient low volume hot top com
the entire surface of the latter remote from said lining
prising a metal casing provided at its lower end with an
with both of said layers having a thickness substantially
inwardly extending ?ange, a lining in said casing con
less than the thickness of said lining.
tacting and supported on said ?ange and formed of porous
rather fragile insulating ?rebrick having high insulating
and low heat absorption properties, a single use refractory
bottom ring on the lower end of said casing having a
?rst portion underlying and contacting said ?ange and a
second portion extending inwardly of the hot top beyond
25
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,821,000
Nouveau ____________ __ Jan. 28, 1958
protective unit covering the inner surface of said lining
throughout its vertical length and including a hard dense
565,154
Great Britain ________ __ Oct. 30, 1944
essentially nonfragile, self-sustaining refractory layer
525,428
Canada __________ __-__. May 22, 1956
the inner end of said ?ange, and a preformed insertable
FOREIGN PATENTS
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