US2856657A - Insulating cover - Google Patents

Description

Oct. 21, 1958 w. w. uRME-rz 2,856,657 INSULATING COVER Filed May 2, 1956 EXO THERM/C MA TER/AL -3 INVENTOR. @nf/0E@ o@ PM mw@ 14440257? W l/Awfrz n Q I Arron/Veys United vStates Patent' O- 2,856,657 INSULATIN G COVER Walter W. Urmetz,

Norton Company, Delaware Application May 2, 1956, Serial No. 582,102 6 Claims. (Cl. 22-147) Parma, Ohio, assigner to Oglebay Cleveland, Ohio, a corporation of This invention relates to improvements in coverings that are used with solidifying metal castings, particularly ngots and ingot sinkheads.

It is common ingots to place -a hot top on each ingot mold, i

One of the objects of fthe present invention is to provide a more efficient covering than is used today and .thereby put a greater percentage of the ingot weight into sound product.

A further object of the invention is to provide a packaged covering which will insure measured amounts of insulating and exothermic materials being used on each ingot. Present practice of throwing loose, granular or :a package which disintegrates to successively deposit a definite quantity of exothermic compound on the molten metal, and also provides a divider or diaphragm surmounting the exothermic layer which will-not collapse as the molten metal level drops during the contraction of the solidifying ingot, said diaphragm supporting a layer of highly insulating, but not self-supporting material.

A further object of this invention is to provide an insulated diaphragm across the top of the ingot to prevent circulating air currents from carrying away heat from the molten metal as it feeds downward and creates a cavity in the hot top metal.

Reference should be had to the accompanying draw ings forming part of this specification in which:

Fig. 1 shows in sectional ingot mold with a hot top associated with the upper end of the mold, t-he mold and hot top having had molten metal poured therein, and a cover embodying the invention herein, supported upon the top of the ingot.

' use.

has been placed in the box .and the divider 10 placed elevation a portion of an ICC showing a form which the Fig. 4 is a fragmentary section on the line of Fig. 3; and

Fig. 5 is a sectional elevation similar to Figs. l and 2, showing the position of the elements of the cover at some instant during solidication of the ingot.

The cover per se, comprises a box 1 made up of a rigid or self-sustaining combustible material having bottom and side walls 1a and formed in two portions 2 and 2a, preferably joined with the end wall of the container or box and being folded over into the position which is shown in Fig. 3, when the contents of the box have been placed therein.

Within the lower portion of the box is placed a desired quantity of exothermic compound 3. Suitable exothermic compounds are well known in the art and no particular description thereof need be given.

engages the sides of 'the box 1, which box may be prot vided with -a shelf incorporated into the side walls 1b lto receive the divider 10.

Above the divider 10 is a body of insulating material 5 evenly distributed over the same. The insulating material 5 may be asbestos fiber, asbestos board,` SileO-Cel, insulating grog, or any suitable material for the intended When the desired quantity of exothermic material 3 over the exothermic material and the insulating materials placed `on top of the plate, then the flaps 2 and 2a of the box 1 are closed and sealed producing a package, and which can tion or breakage `and which is easily handled when the cover is placed upon the molten metal surface.

By pressing inward either or both of perforated tabs 6 or 6a, a long handle can be slipped under the flaps 2 or 2a and the cover reached over and released into a hot top which has been iilled with molten steel. Alternatively, the tabs may be on the side walls of the cover, as the one shown at 6.

Upon contact with the molten steel the combustible box ll will burn instantaneously and release the exothermic material 3 onto the molten metal surface. ignites and reacts to generate heat which prolongs liquidity of the molten steel in the hot top. The divider 10 becomes a diaphragm or cap whose edges rest upon the rim of solidified metal frozen ragainst the inner surfaces of the hot 'top as is shown in Fig. 2. Divider 10, as a cap, is heated to a very high temperature and would radiate much heat to the atmosphere above the cover', if it was not for a iayer of insulating material 5 resting upon it. As molten steel in the mold volume or shrinkage occurs, molten steel feeds downwardly from the hot top to satisfy this shrinkage, and the molten level in the hot top drops.

With the usual granular or powdery covering materials of the present art, the lowering 4of the molten level in the hot top would be accompanied by descent of the covering material. This condition would expose the frozen sidewalls of the forming sinkhead to radiate heat to the atmosphere and allow convection currents of cold air to enter the. cavity and carry away more heat.

'Patented' Oct. 21, 1958 different components of the 1b, and a flap closure which is these portions being Over .the exothermic t, compound 3 is placed a rigid partition or divider 10, which assumes the form of a plate and may be of thin steel sheet t `or may be of ceramic material or be 4shipped with a minimum ofI contamina` This material solidifies, a contraction of ln this invention, the reaction products of the exothermic compound ride the'lowering level of the molten metal as an intermediate insulation between the molten metal land the cap formedl by divider 10. The latter plus its insulating layer Sprevent convection currents and minimizes radiation losses from the molten pool and the solidified yshell 7a as shown in Fig. 5.

The use of the insulating cover herein described,.mini mizes heat losses through the open end 4of the hot top, and reduces the amount of molten steel needed in the hot top to produce a sound ingot.

Customarily, the amount of molten steel poured into a hot top is 15 to 20percent -of the total poured into both mold and hot top. The amount of molten steel fed out of the hot top into the solidified ingot is 3 to 5 percent of the total metal poured into the mold and hot top. This isralways needed to produce sound ingot and miximum amount sound product rolled from `the ingo-t.

The difference between the 15 to 20 percent and the 3 to 5v percent is lthat amount of molten steel wasted by the inefficiency of the hot top in making available the 3 to 5 percent. This inefficiency is inherent and is attrib uted to the heat capacity and conductivity, of the hot top mass, land heat loss through the top end of the hot top.

For a lixed hot top construction only, the heat loss through the top end can be minimized, and the insulating cover herein described reduces such losses markedly as is shown by results obtained by plant trials.

A certain hot top and mold combination covered with a proprietary exotherrnic covering produced an 8380 pound ingot, of which 7120 pounds of molten steel were in the mold and 1260 pounds in the hot top. This latter was 15 percent of the total ingot.

The same hot Itop and mold combination requiring 7120 pounds, of molten steel in the mold, only required 1060 pounds of molten steel in the hot top (13 percent of the total ingot) when covered with the insulating cover herein described. A savings of 200 pounds of steel per ingot was made. For this particular practice, the open hearth furnace produced 41 ingots with the conventional cover `and 42 ingots with the cover of this invention.

The increase in productivity `did not require additional melting capacity. Uniform covering practice was obtained. A cleaner operation resulted. Human judgment las to how much, and how well distributed would be a loose material thrown on an ingot would be eliminated in favor of measured amounts positively emplaced.

Having thus described my invention, l claim:

l. A heat retaining unit for use as a cover in the open upper end of a mold or hot top in which molten metal is east comprising a layer of predetermined thickness of loose exothermic material, a rigid non-combustible divider plate separate from said layer of exothermic material and overlying the latter, a layer of predetermined thickness of loose insulating material separate from but overlying said divider plate, and combustible container means for said layers and said divider plate whereby when said unit is used said container means is destroyed by combustion and said exothermic material falls onto the molten metal and into 'the shrinkage cavity that forms las the molten metal cools while said divider plate bridges the shrinkage cavity Iand supports the layer of loose insulating material above said cavity and above the upper end of the cooling metal in the mold or hot top.

2. A heat retaining unit for use in the open upper end of a mold or hot top in which molten metal is cast comprising a heat destructible box of a size and shape to substantially intert the said open upper end of the mold or hot top and engage the upper exposed surface of the molten metal therein, la layer of predetermined thickness of loose exothermic material in said box covering the bottom thereof, a rigid -non-combustible divider plate interitt-ing the interior -of said box `and separate from said layer of exothermic mate-rial and overlying the latter, and a layer of predetermined thickness of loose insulating material in said box separate from but covering and supported by said divider plate whereby when said unit is used said box is destroyed by combustion and said exothermic material falls onto the molten metal and into the shrinkage cavity that forms as the molten metal cools while said divider plate bridges the shrinkage cavity and supports lthe layer of loose insulating material above said cavity and above the upper end of the cooling molten metal in the mold or hot top.

3. A heat retaining unit as defined in claim 2 and wherein said box is provi-ded with closure flaps coveringv the layer of loose insulating material whereby the contents of said box are protected and the unit can be handled effectively during shipping and storage and use withv minimum of likelihood of damage thereto.

4. A heat retaining unit as defined in claim 2 and wherein said divider plate is of thin sheet metal.

5. A heat retaining unit as `defined in claim 2 and wherein said divider plate is .a ceramic plate.

6. A heat retaining unit as defined in claim 3 and wherein said box is provided with displaceable tabs for the connection of a handling t-ool to said unit to facilitate its placement on top of the molten metal in the mold or hot top.

References Cited in the le of this patent UNITED STATES PATENTS

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