US2462256A

US2462256A - Insulating cover

Info

Publication number: US2462256A
Application number: US626264A
Authority: US
Inventors: Walter M Charman; Benjamin F Anthony
Original assignee: Ferro Engineering Co
Current assignee: Ferro Engineering Co
Priority date: 1945-11-02
Filing date: 1945-11-02
Publication date: 1949-02-22
Anticipated expiration: 1966-02-22
Also published as: BE468545A; FR934444A

Description

Feb. 22, 1949.

w. M. CHAR-MAN EI'AL 2,462,256

INSULATING COVER Filed NOV 2, 1945 w INVEN TOR.

. M6402: M CHAR/WAN By BENJAMIN fi' flnnvo/vy fin Z11 wol/fiouflliql rra Patented Feb. 22, 1949 s PATENT [OFFICE INSULATING COVER 1 Walter M. Charman, Shaker Heights, and Benjamin F. Anthony, Cleveland Heights, Ohio; said Anthony assignor to The Ferro Engineering Company, Cleveland, Ohio, a corporation of Ohio Application November 2, 1945, Serial No. 626,264

(Claims. (01.22-14'7) This invention relates to improvements in insulating covers, that is to say covers for solidifying metal castings, particularly ingots, sinkheads, feeders and risers constituting reservoirs for liquid metal from which the metal may flow into the shrinkage cavities of the castings. Normally the side walls of these reservoirs are less chilling than those provided for the casting or ingot bodies, but the top of the casting frequently has not protection against the loss of heat. If no cover is used the molten surface soon crusts over. The chilling effect of such a crust on the remaining molten metal in the reservoir is such that a succession of crusts may form, all

requiring surplus/metal over that which would be required merely to feed the shrinkage cavity. Heretofore efforts have been made to minimize this heat loss and consequent metal loss by covering the sinkhead, feeder or riser with inv sulation. either in the form of loose bulk materials which can be placed or scattered over the top surface of the molten casting or in the form of slabs which may be laid on the metal surface. When loose material is used it rides the receding molten surface as the sinkhead metal feeds the casting or ingot, the major part of the material collecting at the bottom of the cooling sinkhead. In the course of the formation of the cavity the area of exposed metal from which heat can escape is increased by the addition of the sloping sides of the cavity. The fine insulating material does not coat the slopes effectively. Hence loss by conduction to the solidifying cavity walls and thence by radiation and convection becomes appreciable. For the reasons stated. a fine material of bulk nature, while saving some feed metal, has definite limitations.

The slab type of covering has certain inherent advantages. It is convenient in that it is molded or cut to size to fit a particular hot top or other reservoir, and in use the workman merely drops a slab onto the molten metal of each casting. Also the insulation material in each slab may be accurately measured and evenly distributed when the slab is manufactured, whereas loose bulk material must be shoveled or tossed onto the surface of an ingot for example, the amount and distribution depending solely upon the judgment and care exercised by the workman performing this duty.

A slab which is sufliciently resistant to heat to stand up without failure in use, bridges over the sinkhead at the top of the shrinkage cavity. The surface of the molten metal in the sinkhead is thus left bare and the slab is exposednot only to radiation from the sides of the cavity but .to direct radiation from the receding molten 'upon the use of loose bulk material as well as those inherent in the slab form of covering. The cover of our invention retains its shape in use, remains as a bridge over the shrinkage cavity, and deposits comminuted insulation material directly onto the receding surface of the sinkhead. In addition it may embody at least some of the features of the covering disclosed in our copending application Serial No. 607,590 filed July 28, 1945, including the use of material on the upper side of the slab which expands laterally as well as vertically and thereby effectively closes any clearance between the edges of the slab and the hot top walls.

A general object of the invention therefore is the provision of an insulating cover for the reserve supply of molten metal provided to feed metal into the shrinkage cavity of an ingot or other casting.

Another object is the provision of such a cover of the rigid slab type wherein is incorporated means. responsive to the heat from the molten metal of the casting. for releasing material carried upon the lower side of the slab and depositing it upon the surface of the casting in the form of finely divided ash or other nonfusing substance.

Other objects and features of novelty will appear as we proceed with the description of that embodiment of the invention which, for the purposes of the present application, we have illustrated in the accompanying drawings, in

which Fig. 1 is a somewhat diagrammatic vertical sectional view through an ingot mold and hot top, showing the insulating cover of the present invention when first deposited upon the hot metal of a sinkhead.

Fig. 2 is a similar view showing the condition to that shown at IS in Fig. 1.

of conventional form, in which is positioned a composite hot top comprising a metal casing in two parts II and I2 suitably secured together, a semi-permanent refractory lining in two courses l3 and I4 and a bottom ring l5 adapted for single use. The details of the hot top however form no part of the present invention.

In the formation of an ingot the pouring of the molten metal is continued until it rises to a predetermined level in the hot top, for example Soon thereafter the workman deposits on the surface of the metal a slab IT. This slab is formed to a size somewhat smaller than the opening at the upper end of the hot top, so that the slab may be readily inserted through that opening.

The slab itself is constructed in three layers. The central layer I8 is the one which gives strength to the slab. Its composition may vary to some extent. However it includes preferably incombustible fibers, asbestos for example, an incombustible filler and an incombustible bonding agent, all intimately commingled, molded and,

dried. The incombustible fibers serve to reinforce the slab. The filler may be sand, cinders or other like material and the bonding agent may be clay, cement, sodium silicate or the like. These materials may be mixed in a wet or dampened state, molded and dried. These central layers may be molded individually tothe size desired, or the mixed constituents may be pressed into large sheets and later cut into pieces of the desired size. In any case the layer in question must be of a composition and of a minimum thickness such that when dried it will possess considerable strength, not only to resist deterioration from heat but also to permit handling, shipment and storage without breakage.

The upper layer 19 of the slab is one in which is incorporated ,a considerable percentage of insulating material, preferably insulating material which will expand markedly under the influence of heat. The layer l9 may contain a combustible or incombustible filler and a bonding agent, the latter serving not only to bind the filler and insulating material together but also to. make it adhere to the layer It. While the insulating material of layer is may be one of the usual materials employed for the top of a sinkhead, we prefer to use vermiculite in its natural state, as described and claimed in the above-mentioned copending application. In its natural state vermiculite is flaky and low in bulk, but when heated it exfoliates, the flakes expanding into accordion-like bodies and forming a mass of great porosity and great bulk. The expansion takes place in all directions, so that the height of the layer is increased and the clearance between the edges of the slab and the encircling walls of the hot top is taken up, as indicated in Figs. 2 and 3 of the drawings.

The lower side of layer l8 has a relatively thick coating forming a third layer 20, which may be made up of any material which, after being subjected to the heat of the molten metal, will disintegrate and be deposited upon the surface of the metal beneath it and will in that state con-, stitute insulation. The consituents of layer are of course intimately commingled so that the insulation resulting from disintegration will be evenly distributed over the surface of molten metal in the sinkhead. The layer is composed of relatively non-fusing material containing either combustible or incombustible filler, or both, and a heat destructible bond, for example, pitch,

oii,.corn-flour or glue. The filler materials may be either neutral or exothermic. Suitable inert fillers are comminuted slag, rock wool, sand or ashes. Exothermic fillers should be slow burning or charring such as coal, coke, sawdust, hulls, stalks, straws or any combustible wastage. When the bond is destroyed by the effect of heat the combustible fillers burn or char and their ash, together with any particles of inert filler, is deposited upon the surface of the metal as indicated at 20', and rides down with the metal as the formation of the shrinkage cavity progresses.

It should be noted that. the formation of a slab in distinct laminations is not essential, as one or both surfaces of a self-sustaining slab may be impregnated, the top side with expandable insulation material, and the bottom side with a material which is powder forming under the action of heat. In the latter case some of .the self-sustaining material may then disintegrate and be carried down on the receding surface oi. molten metal along with the powder forming substance.

It will be observed therefore that in the use of the invention there is provided a blanket of insulating material in direct contact with the molten metal in the sinkhead, efiectively insulating those portions, and an insulating cover over the top of thesinkhead which intercepts heat of radiation or convection emanating from the inside walls of the sinkhead to which only small amounts of deposited material 20' cling. The over-all effect therefore is to conserve more heat than it has been possible to do heretofore, and thereby make effective for flow into the piping of the ingot a greater proportion of hot top metal.

In other words the amount of metal which it is necessary to provide in the hot top for a given ingot maybe materially reduced, by the practice of the invention, as compared with that required heretofore.

Having thus described our invention, we claim:

1. An insulating cover for a solidifying ferrous metal casting, which comprises a slab one layer of which when subjected to the action of heat from the molten metal is substantially infusible, incombustible and self-sustaining, said layer comprising incombustible insulating fibers, an incombustible filler and an incombustible bonding agent and another layer of which comprises adherent material on the lower side of said one layer, said adherent material comprising a filler and a heat destructible bonding agent and being adapted to disintegrate in the presence of heat from said metal and to deposit insulating particles upon the surface of the casting which follow the metal of the latter downwardly as the formation of the shrinkage cavity progresses.

2. An insulating cover for a solidifying ferrous metal casting, which comprises a slab one layer of which when subjected to the action of heat from the molten metal is substantially infusible,

incombustible and self-sustaining, said layer com-' prising incombustible insulating fibers, an incombustible filler and an incombustible bonding agent and another layer of which comprises adherent material, on the underside of said self-sustaining layer, said adherent material comprising comminuted incombustible insulating material and a binder destructible under the action of heat from the molten metal, said adherent material being adapted to disintegrate when subjected to the heat of the casting and to deposit insulating. particles upon the surface of the casting so as to reduce the amount of heat radiated from the casting to the slab.

3. An insulating cover for a solidifying ferrous metal casting, which comprises a slab having a rigid layer which when subjected to the action of heat from the molten metal is substantially infusible, incombustible and self-sustaining, a layer of insulating material carried on the upper side of said rigid layer and a third layer comprising adherent material on the lower side of said rigid layer, said third layer comprising a combustible bonding agent and a filler and being adapted to 6 it is to be used, and wherein the incombustible material carried at the upper side of said rigid layer is unexpanded vermiculite, whereby exfoliation of the vermiculite will cause expansion laterally as well as upwardly for completely closing the cavity and insulating the upper end of the casting.

WALTER M. CHARMAN. BENJAMIN F. ANTHONY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 7 Name Date 1,920,854 Gathman' Aug. 1, 1933 1,989,096 Jones Jan. 29, 1935 2,076,898 Labus et a1 Apr. 13, 1937 2,165,945 Seaver July 11, 1939 2,183,424 Clark [Dec. 12, 1939 2,209,519 Halbrock et al July 30, 1940