US 2301101 A
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1 0 6 7 'm qtxammer 1942- L. T. WELSHANS 2,301,101 0 p HOT TOP Filed Sept. 26, 1940 imp-am w Patented Nov. 3, 1942 UNITED STATES PATENT I OFFICE HOT TOP Lewis '1. Welshans, Charles Town, W. Va... assignor to The Standard Lime and Stone Company, Baltimore, Md., a corporation of Maryland Application September 26, 1940, Serial No. 358,558
Claims. (Cl. 22-147) v This invention relates to hot tops used in con- Wwhich will generate gas in the junction with ingot molds to form a heat inpresence of water by reaction with the alkaline s l ns n i n t th p f h m d, which constituents of the mix. Generally stated, the serves to retain a bath of molten metal at the hydraulic cement is used only in sufficient quantop of the mold during the freezing of the ingot. 5 tity to produce the necessary binding action and T efie t s to p event or minimize piping and selected with reference to its setting characthe formation of other defects in the head of the terlstics to assure the desired porous texture.
ingot. The quantity of powdered aluminum or its equiv- In a p r pp y pplicants alent is determined on the basis of attainment assighee. and identified as Serial l of the desired porous texture. The texture is filed June 30, 1939, in'the name o'f I. A. Nicholas, also affected by the setting time of the cement there is described a hot top which is a decided and the two must be suitably coordinated for improvement over the fire clay hot tops and the b t're ults v g fire brick lined metal hot tops commonly used When molten steel comes into contact with a in the art. The present invention is in the nahot top of this type, the carbonate will partially ture of an improvement on the Nicholas invendecompose leaving a powder of magnesium oxide tion. or calcium oxide both of which have excellent T imp v h p r er disclos h insulating properties. The effect is to improve a number of adv nt s Compared to prior art the heat insulating characteristic of the hot top hot ps. These are: lightness, w c Permits a during its use. Upon stripping, very little of the saving in the la'bor'flf P ac ng the hot top; case material of the hottopadheres to the ingot, of manufacture from inexpensivematerials with and uch as does adhere can readily be dislodged direct production economies; markedly increased by poking with a rod. Any residue not dislodged heat insulating characterlstics;' and the charreadily falls off in the blooming mill rolls, and
acteristics of partiallydisintegrating at temperais not harmful tothe mill scalef Mill scale is tures of molten steel with the result that porused in hast furnace and open hearth operations of the hot top adhering to the ingot may tions where its purity is an important factor. be readily removed. Perhaps the most import- However, theresiduefrom the improved hot top ant characteristic is; the fact that the material improves the smelting properties and, therefore, which forms the major component of the'hot its presence is not objectionable whereas the top is not harmful to the mill scale produced presence of even small amounts of fire clay is during the rolling of the ingot. On the conmost seriously objectionable. tary, it is beneficial. The above being the general principle of the The fire clay hot tops heretofore universally invention, the preferred mode of carrying it out used are extremely difficult to remove when porwill now be described in connection with the tions of them adhere to the ingot. This entails accompanying drawing in which: substantial labor costs in removal and when, as Figure 1 is a perspective view of the hot top ';is often the case, the removal is not complete, made up of four identical slabs cast from the the adhering fireclay is harmful to the ingot material in question and connected by twisting and even more harmful tothe mill scale protogether certain protruding reinforcing wires duced during rolling. 7 Since mill scale is a comwhich are cast in the slabs; v mercial by-product of substantial value it is im- Fig. 2 is a'plan view of the hot top in posiportant that it not be contaminated. tion on the top of an ingot mold;
'According to the present invention the light- Fig. 3 is a vertical axial section of the upper ness of the hot top is increased by imparting portion of the mold with the hot top in place; a highly porous characteristic to the hot top Fig. 4 is a face View of one of the slabs inor to the component slabs of which it may be dicating the locationtof one form of reinforcecomposed. The material of which the not top ment; and f is composed comprises at least one basic car- Fig. 5 is a section through one of the slabs in bonate such asmagnesium or calcium carbonate, M the mold showing how the reinforcing material either artificially p pared or as they occur in is placed and may be, positioned during the slab nature. Dolomite may also b used. Suflicient casting operation. hydraulic cement such as Portland cement is The first step is to prepare the mix from which used as a binder, and with this Portland cement the slabs or hot tops are to be cast. Although a is used a gas generating substance such as pgysectional hot top made up of slabs is shown and is preferred, certain advantages of the invention can be had with hot tops cast in one piece as heretofore proposed.
A typical example using limestone as an ingreclient will now be given: Limestone as it occurs 5 in nature is pulverized and screened to a size under 8 mesh and over 60 mesh. To the pulverized limestone is added Portland e'ement in approximately equal quant ty y weight. To these two ingredients is added 0.2% by weight of powl dered aluminum. To the three ingredients above described an amount of water is added equal to about one-fourth of t eir combined weight.
The ingredients are mixed-in an ordinary con -w..-
crete mixer. The resulting slurry is rather thin and can readily be poured into forms or molds to harden.
100 pounds as compared with the weight of 200 pounds, or more, characteristic of the commercial hot tops of the prior art. The us of four slabs which are assembled to form the hot top reduces the storage space to about one fifth of that required where the hot tops are cast in one piece.
To produce the hot top, four slabs I4 are as- ;sembled as in Fig. l, and the wires l l are twisted together as indicated at I 5 and "thus connect the four slabs into a substantially unitary hot top. The hot top so formed is then inserted in the top of the ingot mold generally indicated at IS "in Figs. 2 and 3. The twisted wires I5 of the lower set engage the upper end of the ingot mold l6 and serve to sustain the hot top in position.
It'has been stated that the material of which The powdered aluminum-reacts with the. water and the alkaline constituents of the mix to libcrate gas which is trapped in the mix and causes pulling or swelling, resulting finally in alight weight porous slab. The swelling action 'ordi narily commences within fifteen minutes and the 'slabswill have set sumciently'within a flew pe rs to permit their removal fromthe forms. .After removal, they are allowed meme, three days being considered thenfiinir'num curing period. The slabs are then dried until their water content 'is reduced to 1% or less',',.f This can be conveniently the slabs are composed tends to disintegrate at ,the temperature of molten steel. It should be explained that this disintegration is partial, and not attended by any danger, for the reason that afthin shell oi steel instantly freezes within the hot top. contrary to prior belief, substantial mechanical strength of..the hot top is by no nieansne'cessary. .A crushing strength of 10 accomplished by 'treat'ing'them inia drier atv approximately 600?,Fifor twenty fourhours The resulting 'slabs' are. marl edly porous and of suiilcient strength to withstand shipping and handling. If stored,. .they should be kept dry and in a dry atmosphere, for they have .a tendency to absorb moisture fromlthe atmosphere. Excessive moisture in the slabs is objectionable during use because'it causes the metal to 'boil.
. some reinforcement is desirable an d li prefer to use a steel wiremesh fabric. hexagonal D mesh wire fabric of conventional weave is satis factory. For slab-connection purposes I also use reinforcing wirestrands which can besustained by'fthe wire mes ur ng the casting operation,
which will nowbe'explained in some detail, slin- 4 cedure, In'Fi 5a portion of an open'top mo ld is in:- dicatedjat'B. Before the casting op'erationla ply'to disclose on commercially practicable prowire mesh fabric, indicated generally by the numeral I, is placed in the moldand maybeisus tained by bending down strands 'of the mesh at the edgeas indicated at 8, Strands of somewhat the mesh with their end portions I b'ent, outward sheet of reinforcing.inaterialfsuch as hexagonal heavier wire indicated at '9 may be interlaced in 5 so that they willprotrude from the slab as dicated mor clearly iri Ffig. 4.
" The slurry or mix above described is poured in to the mold,.the'quarit it'y being suchthat after the swell takes "place, the mold will be filled approximately to the lev el i Z (Fig. 5). The overhanging end l3 of the mold which produces the rounded end or illlet' at onejnd of the slab may be made removable to facilitate. removal of the slab from the mold after ithasfset. The result ing slabs can all be identical in si'z e.. Such slabs are generally indicated by the numeral l in Figs.
sizes of slab will suflice, one about 22 5 by 15", and the other about 16 by 15", the thickness being of the order of 2", though thinner slabs can be used. Four slabs of the larger size and of the 2" thickness stated, have a weight of about to 15 pounds per squareinch obtainable with the porous slabs of the present invention is adequate despite the fac'tf'that .the' burned clay hot tops heretofore used had crushing strengths in some instances as highas 1500. pounds per square -The insulating properties ioffithe slabs are at tributable to their porous or cellular texture and also to the inherent insulating properties of the pulverized ingredient which is used with the hydraulic cement. The preferred. pulverized inbroad contemplation of the invention to use any other pulverized insulating material which will not react with the metal being cast or whose reaction therewith is tolerable. The described carbonates areg believed' to be thebest available ma- The porosity and cellular texture may be produced in any known way, but the addition of the' small percentage of aluminum is convenient and satisfactory. On the whole, aluminum is believed to be the best available substance because it can be readily obtained at amoderate price, r a has no objectionable reaction with the steel anddoes not begin to develop gas toosoon orftoo u nly. Asa practical matter, it is desirable V Y that t e evolution of gas commence some minutes after the water has been added to the mixture, thus affording'ample time for mixing and pouring. The time of evolution of the gas is also "important with reference to the setting time of the cement for evolution'should commence beforesetting startsand should be sotimed as to secure the desired degree of porosity with the minimum reaction material. .As a rule, use of one of the well know-hi quick setting hydraulic cements is considered preferable.
A satisfactory slab can be produced by the ,use' of the proportions outlined, but it must be understood that they are illustrative and not limiting. The eii'ort is to use as little cement as isrequired for the bindingefi'ect and as little gas generating Regent as is necessary for the We... m- 5' Examiner :.zsn s|- n d desired degree of porosity. This permits availing to the maximum degree of the desired chemical and heat insulating properties of the carbonates.
It should be fully appreciated that the important function of a hot top is to maintain as long as possible the molten condition at the top of the ingot mold and to avoid any harmful reaction with the molten metal. Consequently, the porous cellular structure, because of its markedly superior insulating qualities, represents a decide advance in the hot top art.
In its broadest aspects the invention contemplates the use of the porous material in hot tops of any form, and in its more specific aspects involves its use with the suggested slab construction and with the reinforcing and connecting stays as set forth. As has been suggested, considerable latitude in choice of materials and modification of proportions and time of drying are permissible.
What is claimed is: v
1. In combination with an ingot mold, a cellu lar insulating hot top supported by and forming a continuation of the top of said mold, said hot top comprising the reaction product of a slurry of a pulverized basic carbonate, a hydraulic eement, and a powdered metal which in the presence of water will react with alkaline ingredients of the slurry to generate porosity inducing gas,
"said hot top having the property of disintegrating ing a continuation of the top of said mold, said hot top comprising a porous cellular mass of concrete in which the aggregate is pulverized limestone bound by hydraulic cement, the concrete containing voids formed by gas bubbles evolved during the setting of the cement and serving to increase the heat insulating properties of the mass.
3. In combination with an ingot mold, a cellular insulating hot top supported by and forming a continuation of the top of said mold, said hot top comprising a cellular mass consisting essentially of basic carbonate and hydraulic cement in substantially equal proportions, and having the property of disintegrating to powder form when subjected to the heat of the molten metal poured into the mold.
4. In combination with an ingot mold, a porous insulating hot top supported by the mold and forming a continuation of the mold top, said hot top being made up of separate slabs of cellular concrete comprising a fine aggregate in the form of a basic carbonate and a bond in the form of hydraulic cement.
5. In combination with an ingot mold, a porous insulating hot top supported by the mold and forming a continuation of the mold top, said hot top being made up of assembled slabs each comprising a cellular mass of pulverized basic carbonate and hydraulic cement and having the property of disintegrating to powder form when subjected to the heat of the molten metal poured into the mold.
- LEWIS T. WELSHANS.