US2390500A - Low volume sinkhead - Google Patents

Description

Dec. 11, 1945. w. M. CHARM AN ET AL 2,390,500

LOW VOLUME SINKHEAD INVENTORS WALTER M. CHARMA/v BENJAN/N f7 ANT/MN! 5y M MN & M

A T TORNE Y5.

Patented Dec. 11, 1945 was I Low vou'nun smnnmn Walter M. Charman, Shaker Heights, anwn iamin F. Anthony, Cleveland Heights, Ohio;

said Anthony assignor to Fem Engineering,

Company, hio

Cleveland, Ohio, a corporation of Application July 30, 1942, Serial No. 452,848 2 Claims. ((122-147) This invention relates to low volume sinkheads and to hot top apparatus for producing sinkheads or that character. More particularly, the

invention relates to the art of hot topping or feeding metal ingots and castings, and is concerned with the attainment of eillcient feeding or hot topping by smaller amounts of feed metal than hav heretofore been considered practicable.-

Well known in theart is the fact that the hot top or riser maintains the metal in the sink.- head or feed head of the ingot or casting molten long enough to feed the shrinkage or contraction cavity, commonly known as pipe. Conventional steel ingot practice requires that the hot top receive from twelve per cent to twenty-four per cent by volume of the molten metal in the entire ingot to satisfactorily produce a sound, relatively segregation free ingot body available for commercial product. This variable volume depends upon numerous factors, such as size and shape of molds, molten metal temperature and analysis, and pouring practices. satisfy the shrinkage characteristics or the ingot may range from four per cent to eight per cent while the remaining metalin the sinkhead is that which must of necessity be present in order to take care of heat losses and thereby make available the small quantity required for feeding pipe. Thesolidified metal making up the sink-- head is not commercially usable, due to its shape, porosity, impurities. and segregation, and this in- .vention is directed towards reducing the amount of molten metal which must be fed into the hot top or feed head in order to effect elficient hot topping or feeding with a minimum of discarded metal.

or the hot top in order head diiring the active life of the latter may be reduced.

Another object of the invention is the provision of simple means for decreasing the cross-sectional area of the space enclosed by the hot top,

'Still another object is the provision of auxihary lining means containing exothermic material capable of giving oil heat at a relatively low rate in order to delay solidification of the metal in the sinkhead, more particularly in the lower portion thereof.

Other-objects and features of novelty will ap- The amount of molten metal to pear a we proceed with the description of those embodiments of the invention which, for the purposes of the present application, we have illustrated in the accompanying drawing, in. which Figs. 1 and 2 are diagrammatic views principally in vertical section, Fig. 1 showing a conven-- tional sinkhead and Fig. 2-showing a sinkhead formed in accordance with the present invention. Fig. 3 is a vertical sectional View throughv a fragment of an ingot mold with an ingot therein and a compositehot top embodying the present invention. v I

'Figs. 4 and 5 are similar views of modifications, and

Figs. 6, '7, and 8 are similar views of mold appa- The sinkhead therefore includes a large mass of metal at and near its lower end particularly. In.

Fig. 2 the cavity l3, instead of being V-shaped in cross-section, is U-shaped, that is to say, the sinkhead has thinner walls and the metal content is much less than in Fig. 1. The production of a sinkhead of the general characteristics of that illustrated in Fig. 2 is the end sought by the invention. l

In Figs. 3, 4, and 5 we haveillustrated a cast metal casing of more or less conventional form having upwardly tapered inner wall surfaces and an inwardly extending ledge ii at its lower end. The hot top is formed to fit within the mold cavity of a mold N which may be of generally circular; rectangular or other cross-section. .The inner-wall of the casing above ledge I5 is covered by a semipermanent refractory lining, which may be a one piece element formed in situ or may be made up of blocks of proper shape fltted,to the casing and keyed inpositlon. The term frefractory" as herein used refers to non-metallic heat I resistant material. a particularly near the bottom thereof, while at the same time the heat loss from that portion ofthe hot top is decreased.

It. Arefractory bottom ring l8, also of conventional form is temporarily supported in known manner from the casing It, as by means of spring clips and covers and protects the lower end of the latter with its ledge II; The ring i9 is iugeneration of gases in eration of topsurface of the metal ring l9 except the casing and stays with the ingot when the hot top is stripped therefgom. Inwardly of the lining course l8 we provide huxiiiary lining means 20 of'a with the inner'surface of the lining course I! and the inner surface of bottom ring l9. This auxiliary lining 20 may be applied in paste form and permitted to dry thoroughly before-the hot topis used. or it may be preformed in one Or a plurality of pieces and dried before being placed in the hot top. j

The composition of this auxiliarylining means may vary. It should include some exothermic compound. Its exothermic action should be relatively slow in order to extend approximately over the period of time required for the freezing of the ingot body. As a rule its exposed surfaces should be sealed off with a substantially impervious coating to prevent the escape of gases into the molten metaluntil a thin shell has been formed thereof, although in some cases it'may be advisable to provide vents for the discharge of such gases. However, the aforesaid impervious coating plus the low degree of exothermicity or combustibility of the auxiliary lining prevents the such quantity as to make hazardous the filling of the hot top or to contaminate the molten ingot.

While we do not wish to be limited to the use of any particular material or combination of materialsin the construction of the auxiliary lining means, we may mention as possible compounds, sources of carbon such as coal, coke breeze, tar and graphite, sources of silicon such I as ferro-silicon, sources of aluminum such as dross, or any other materials which, when'suitably compacted, will in the presence of entrained air or oxygen or oxygen obtained from an included oxidizing agent, oxidize or burn with the libthe desired amount of heat, and at such a slow rate as to counterbalance heat losses from the hot topmetal other body, or adda desired quantity of heat to effect the advantages attained by the invention. The compacting may include sintering, cementing, fusing, or packaging, but in any case, the auxiliary lining should be thoroughly dry and should not be displaceable by molten metal.

Farm or forest. products or by-products in general which will function as heretofore described can be used as constituents of the auxiliary lining. For example, a compacted lining block may be formed of straw or vegetable hulls, such as oats or rice, mixed with a suitable binder, the

lockbeing faced with an inert wash to prevent undue gassing.

escape of heat from the the latter is preferably covered promptly with a layer 2| of exothermic or insulating material, a number of which are readily available for this purpose. Oat hulls, rice bulls and straw may be mentioned. They burn more or less quickly but the ash which. forms builds up a, porous blanket which has an excellent heat insulatingeflect. e

In the Fig. 4 construction a semipermanentlining 22 may be of the same thickness throughout its extent. The bottom ring 23 is similar to the that it projects inwardly beyond this. projecting portion In order to prevent the the face of the lining 22, serving as a support 24 of the same character as the lining means 20 above described. Liningmeans 24 extends upwardly part wayonly of the height of the hot thicknesssuch as to present asurface flush a,seo,ooo tended for single use and ordinarily parts from top and may be of considerable thickness. so that it materially decreases the cross-sectional area of the space within the lower part of the hot top. Hence it tends to reduce the horizontal dimensions of the sinkhead at the same time that it reduces heat lossand thereby tends to lessen the thickness of the sinkhead wall.

than to the ingot j for auxiliary lining means "Fig. 6, but the refractory The auxiliary lining 24 remains upon when the hot top is stripped therefrom, it is not of a character-to harden materially under the influence of the heat of the ingot, it is readily penetrated by the bits of a handling crane.

the meet and these bitsmay be caused to enter it just beneath the shoulders 25 in the sinkhead, thereby providing a secure grip on the latter.

The construction of Fig. 5 differs from that of Fig. 4 principally in that it causes a constriction between the sinkhead and the ingotv proper and tends to reduce still further the horizontal dimensions of the lower part of the sinkhead. Here again the semipermanent lining 28 may be of the same thickness throughout its mount auxiliary lining means 3!, which is preferably preformed to fit within and be supported by the member 30. v

The Fig. 7 construction is similar to that of the same thickness from top to bottom, while the preformed auxiliary lining means 33 has an outwardly directed flange 34 at its upper end to rest upon the upper end der to provide a support for the auxiliary lining means. In this construction as well as in the construction of Fig. 6 a constrictionis formed at the junction of the sinkhead and the ingot proper.

lin the form of the invention illustrated in Fig.8 the one piece shaped somewhat like .an inverted mushroom, that is its walls are flared outwardly at the lower end so as to approach closely the inner surfaces of the mold It. The upper part of the hot top may be a cylinder of comparatively small diameter, so as to reduce the horizontal dimensions of the sinkhead, and it may have recesses 38 at oppositely located positions in order to provide projectionson the sinkhead under which crane bits may effect a good grip. The auxiliary lining means 31 in thiscase is applied to a the molten metal being 'poured into the mold rises therein to the height previously determined.

upon. A layer of insulation or exothermic material is then deposited upon the surface of the molten metal as indicated at 2|, and the hot top supporting blocks are knocked out, permitting" the hot top to float with the inset. The metal in the conventional a longer time than that in the mold proper, due tov the insulating effect of the semipermanent lining in the case of a composite top or to the baked refractory of which one piece hot tops are and since extent, and its ,lower part is covered by auxiliary lining means hottop-fl may be of.

of the member 32 in orrefractory hot top 35 is the mold until hot topremains molten for made. It is unavoidable that some heat should be dissipated through these refractory enclosures,

and it is impracticable to prevent such loss en- Q tirely, but by ourinvention this heat loss is compensated to a considerable extent at least, that is to say when the hot metal strikes the auxiliary lining means containing exothermic material,

slow combustion is caused to take place and heat is given of! to replace the heat loss through the hot top walls. The'metal in the hot top or in the lower part .of the hot top therefore remains molten longer than would otherwise be the case, and the tendency for it to freeze inwardly a considerable distance from the outer surfaces oi' the sinkhead, as in Fig. 1, is overcome so that the cavity is widened considerably at the base thereof, as illustrated in the remaining figures of the drawing. A lower volume of molten metal is required to give the desired soundness and cheming refractories as the semipermanent linings which will not withstand contactwith molten l metal, but when-afforded the protection of the auxiliary linings 20, 24 or 21, will provide still more efllcient h dt DP E.

]Having thus described our invention, we 0 aim:

1. In a composite hot top, a metal casing, a semipermanent refractory lining covering the inher wall of the casing, and auxiliary lining means covering the lower portion of said semiperma nent lining for reducing the cross-sectional area of the space enclosed by the lower portion of .the hot top and for decreasing the heat loss from said lower portion.

2. In a composite hot top, a metal casing, a semipermanent refractory lining covering the inner wall of the casing, and auxiliary lining means covering the lower portion of said semipermanent' lining for reducing the cross-sectional area of the space enclosed by the lower portion of the hot top and for decreasing the heat loss from said lower portion, said auxiliary lining meansbeing retained by the I sinkhead when the hot top is stripped from the ingot, and being adapted to be penetrated by the bits of a handling crane.

WALTER M.- CHARMAN. BENJAMII! F. ANTHONY.

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