US1825445A - Hot top for ingot molds - Google Patents

Description

Sept. 29, 1931. M. G. DUMA\S HOT TOP FOR TNGOT MOLDS Filed Dec! 5, 1929 Q 64 '),4- aZ 9\ 3 L i i 6 /0 9 8 yy uz'gpgam Patented Sept. 29, 1931 UNITED STATES MAXWELL GERSON DUMAS, OF PITTSBURGH, PENNSYLVANIA HOT T]? FOR INGOT' MOLDS Application filed December 5, 1929. Serial No. 411,756.

This invention relates to apparatus for and method of feeding molten metal to ingot molds to prevent formation of piping in the ingots, and the invention is particularly applicable to the hot tops or sink heads for ingot molds and is effective in reducing the size of the hot top and the amount of croppage or waste.

In casting ingots for the use of hot tops, a

mass of molten metal in excess of that re quired to feed the ingot mold is retained in thehot top to constantly feed molten metal to the center of the ingot while it is settling or cooling, thereby preventing the formation of so-called pipes.

The mass, as utilized, is dependent upon the pressure necessary to feed the fluid metal into the mold and since the height of the metal column determines the available pressure, hot tops are usually designed to be of such height as to produce an excess of croppage after the ingot has been cooled.

In accordance with the present invention, mechanical pressure is appliedto the molten metal in the hot top or feeder whereby the height of such hot top and resulting croppage can be materially reduced, thus producing an enormous saving in metal which is otherwise scrapped, and the invention may be practiced with either the so-called refractory or with permanent type of hot top structures, or it may be practiced also by pressure means applied direct on the ingot mold.

The invention will be more clearly understood in connection with the accompanying drawings in which like reference characters designate like parts and in which Figure 1 is a vertical cross-sectional view of an ingot mold, hot top, and pressure device embodying the principles of this invention; Figure 2 is a similar view of the upper portion thereof;

Figures 3 and 4 cross-sectional views of a hot top and pressure device respectively, showing a modified ,form of hot top' structure; and

' Figure 5 a cross-sectional view of a common form of hot top, for illustrating the effects of feeding and shrinkage in relation to the height of the hot top.

In Fig. 5, 1 designates ingot mold; 2 the hot top structure which is of the common straight w'all type having a supporting flange 3 by means of which it is placed on top of the ingot mold. The ingot is shown after solidification of the metal and the pipe 4 in the body of the hot top' portion of the ingot mold is shown to illustrate the proportion of length of hot top to the length of sound ingot in the mold. From a consideration of the length of the pipe in Fig. 4 it is apparent that the hot top is too short to produce a sound ingot all the way to the top of the ingot mold and the proper length of hot top is designated by the dotted lines 5.

It is apparent that if a hot top of the extended length were raised and supported by a flange to bring the line 5 in line with the bottom edge 6 of the hot top, the ingot in the mold would be sound all the way to the top, that is, to substantially the bottom line of the hot top or sink head.

In accordance with the present invention, the length of hot top can be materially reduced by applying a pressure means to the metal within the hot top, as illustrated in Fig. 1. In this view the ingot hold 1 and hot top 2 are filled with molten metal and after pouring, a. refractory plunger 6 is placed thereon which may or may not be provided with a weight 7. Ihe total weight of plunger 6 and the member 7 produces a pressure on 8 the metal in the hot top in excess of the normal pressure available to feed molten metal to the center of the ingot when the metal in the ingot is setting or solidifying.

By the customary practice of pouring in- 8 gots, the necessary pressure as explained herein is provided by producing a given height of column by extending the length of the hot top structure. Since this is the only purpose of regulating the height of the feed metal, the mechanical application of a weight in the manner demonstrated in Fig. 1 will produce an equivalent head pressure for feeding and displacing the metal in the hot top portion of the mold, thus providing a solid and sound ingot for the full height of the ingot mold, whereas the lack of suflicient feed pressure will produce a. porosity at the junction of the upper part of the ingot and the lower part of the hot top.

The metal of the hot top will, of course, so lidify around the inner periphery of the hot top due to heat radiation losses through its refractory wall structure. and this will connteract the presence of the combined weight and plunger, thus requiring a mass of mechanical weight in excess of that to produce a pressure inherent in the molten column of hot top of extended length. and for this reason also the bottom of the plunger 6 is of convex form as at 8 since the tendency of the metal in settling is to-shrink away from the central portion of the mass in the manner shown in Fig.

Fig 2 illustrates the form of the solidified metal as effected by the pressure of the plunger and the weights 6 and 7 which are shown as moved downward to the interior of the hot top and the space 9 illustrates the manner in which the metal shrinks away from the center of the plunger when the weight of the mass is no longer effective on the solidfying metal in the hot top structure. However. at this stage of the solidification, the body of the ingot is already solidified and any piping which has a. tendency to form, will be confined to the metal in the lower hot top portion thus assuring a sound ingot for its total length.

In the modification as shown in Figs. 3 and 4, the hot top 10 is shown with a flared or tapered body portion 11 which produces alarger surface area at the bottom 12 than at the constricted upper portion 13. Accordingly, the pressure exerted on the molten metal in the hot top by the combined plunger and pressure member 6 and 7 is distributed over a larger area at the bottom of the hot top and since according to the law of fluid pressure, the pressure per square inch of area is equal at all points, irrespective of the form of the liquid container, the total pressure available at the bottom will be greater than the applied pressure at the top.

Fig. 3 illustrates the invention with the metal in the hot top in a molten condition and Fig. 4 after the metal has set. The weight member 7 may be provided with a loop 14 by means of which it is manipulated in applying and removing it to the plunger of the feeder.

.By employing a refractory plunger of the type shown at 6, the heat of the mass of molten metal in the hot top is dissipated less rapidly than where the open form of hot top is employed and the pressure of the plunger and weight is effective for a longer period of time than would be the case if the metal at the top of the feeder Would solidify more rapidly. Thus it is evident that the plunger 6 acts as a heat insulating cover as well as a plunger for applying pressure to the metal within the hot top structure.

It is evident from the foregoing description of this invention that the method of applying pressure to the feeder or sink head for ingot molds provides a simple and expedient means for producing sound ingots with a minimum amount of croppage or scrap metal thus greatly reducing the manufacturing costs.

Although one embodiment of the invention has been herein illustrated and described, it will be obvious to those skilled in the art that various modifications may be made in the details of construction without departing from the principles herein set forth.

I claim herein as my invention:

1. The combination with a. hot-top, of a weight the outer dimensions of which is less than the inner dimensions of said hot-top, and a refractory plunger, adapted to be interposed between said weight and the metal in the hot-top, said plunger having its bottom face of substantially convex-shape.

2. The combination with a hot-top having a straight wall portion at its upper end and terminating in a flared body portion at its lower end, a weight the outer dimensions of which is less than the inner dimensions of the straight wall portion of said hot-top, and a refractory plunger adapted to be interposed between said weight and the metal in the hot-top. said plunger having its bottom face of substantially convex-shape.

In testimony whereof I have hereunto set my hand this 4th day of December, 1929.

MAXWELL G. DUMAS.

Images