US2913786A - Sheet metal hot top and method of using exothermic material in pouring ingots - Google Patents

Description

Nov. 24, 1959 w M. FARNSWORTH ETAL 2,913,736

SHEET METAL HOT TOP AND METHOD OF USING EXOTHERMIC MATERIAL IN POURING INGOTS INVENTORS WALTER M. FAK/VSWUKTH Filed April 5, 1956 JACK h. KENNEDY SHEET METAL HOT TOP AND METHOD OF USING EXOTHERMIC MATERIAL IN POURING HIGOTS United States Patent Walter M. Farusworth, Canton, and Jack H. Kennedy,

Waynesburg, Ohio, assignors to Republic Steel Corporation, Cleveland, Ohio, a corporation of New Jersey This invention relates to a method and apparatus for maintaining the metal in the upper part of an ingot mold in molten state after the pouring of the ingot.

As an ingot of metal, such as a steel ingot, cools in the mold and solidifies, it shrinks and generally forms a cavity known as a pipe in thecenter of the ingot. Various methods and apparatus have been employed in an effort to avoid damage to the ingot by formation of this pipe. A frequent device for eliminating such a pipe has been the use of a hot top. Hot tops, in general use, have a refractory lining or are made of a refractory material. The hot tops are placed on top of the ingot mold as an extension of the mold. As the molten metal solidifies in the ingot, and tends to form the central cavity, the metal in the hot top acts as a reservoir to feed the metal into the cavity thus producing a sound ingot. However, when the ingot is subsequently rolled to produced plate or sheet, the portion of the ingot which has remained in the hot top is cut off below the junction of the hot top and the ingot and the hot top portion of the metal is scrapped. The hot top section may constitute from ten percent to twenty percent of the ingot and usually runs between twelve percent and fourteen percent of the ingot.

In the use of the hot top, it is a conventional practice right after the ingot is poured to cover the molten metal in the hot top with an insulating material or an exothermic material which upon contact with the metal reacts to maintain the adjacent metal in molten state. The exothermic materials have been found to keep the metal in the molten state longer, and, therefore, usually permit a lower hot top volume, thus providing a better ingot yield, i.e., the amount of scrap metal in the hot top section is reduced.

Some producers of high alloy steels have used electric arcs and gas heated hot tops to keep the metal molten during the solidifying of the ingot, because in some cases the exothermic materials have been found to contaminate the steel ingot, especially righ alloyed types, such as stainless steel.

' Therefore, although the exothermic materials have been found useful for maintaining high temperature during the solidifying of ingots, the contamination of the ingots by the reaction products of the exothermic materials has been a deterrent to their use.

It is an important object of this invention to provide for a better ingot yield and also obtain ingots which are not contaminated by the reaction products of the exothermic materials and which do not require the equipment expense and other expense of keeping the metal molten at the top of the mold by electric are or gas heating equipment.

Other important objects of the invention will be apparent from a description of the invention.

' The invention comprises maintaining a mass of exothermic material in the upper part of the mold out of Contact with,'but in heatconductive relationship to the sheet metal, e.g. 28-gauge steel.

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metal, whereby the metal is maintained in molten state after the ingot has been poured and during the solidi fying and shrinking of the ingot.

The invention contemplates the use of an apparatus comprising a container extending into the mold from the top thereof, the container being formed of heat conducting material and being filled with a mass of exothermic material which reacts by contact of the molten metal with the walls of the container. It is contemplated that the container in one form will be in the shape of an annular collar fitting closely against the inner walls of the ingot mold and extending down into the mold from the upper end thereof.

-It is also contemplated that means will be provided on the container for supporting and maintaining it in position in the upper part of the mold, the container being readily positioned in the upper part of the mold prior to the pouring of the ingot, the container defining a central opening through which metal may be poured into the mold while the container is in place in the upper part thereof.

For a more complete description of the invention, reference is made to the drawings wherein:

Fig. 1 is a cross-section of the upper part of an ingot mold with apparatus embodying this invention'disposed in the upper part of the mold;

Fig. 2 is a plan view of the form of apparatus shown in Fig. 1;

Fig. 3 is a sectional view taken along the line 33 inFig. 2;'and

Fig. 4 is a cross-section of an ingot mold showing another form of the apparatus of this invention in position in the upper part of a mold.

Referring to Fig. 1, an ingot mold 10 for receiving molten metal is provided with an inner wall 11 and top portion 12, the molten metal being received through the opening 13 in the top of the mold. Disposed in the upper part of the mold adjacent the top 12, is a container 15 comprising an outer wall 16 which is of a size to fit within the upper part of the ingotmold and adja cent the inner wall 11 of the mold. The container form a chamber 20 for receiving a mass of exothermic material.

The container is provided With brackets 22, suitably attached to the outer wall 16 to support it on the upper edge 12 of the mold, as indicated in Fig. l.

The bottom wall 18 may slope upwardly from the outer wall 16 to the inner wall 17, as best shown in Fig. '1. The walls of the container may be made of suitable heat conductive material, such as metal, and for practical purposes, may be made of relatively thin Where the metal of the ingot is an ordinary steel or is stainless or other highly alloyed steel, it appears satisfactory to make the container 15 of ordinary steel or iron. The metal container can be fabricated by welding or can be stamped from sheet metal and the shape of the container may vary as desired. For example, the bottom of the container may be rounded or the container may take a generally V-shape, such as that shown in Fig. 4.

In Fig. 4, the outer wall 26 of the container 27 fits closely against the inner wall 28 of the ingot mold 30.

fit snugly in molds of any shape, e.g. square, round, corrugated, or generally rectangular as shown in Fig. 2.

Prior to the pouring of an ingot into the mold 10, the container 15 is positioned as shown in Fig. 1 in the upper part of the ingot mold.

The molten metal is poured through the opening defined by the inner wall 17 of the container into the ingot chamber 14 of the mold. As the mold is filled to the top with molten metal, the exothermic material in the container reacts to generate a high temperature and maintain the metal in a molten state while the ingot below the container is solidifying.

Exothermic material starts to ignite within a few seconds after the hot top section is completely filled. Such materials ignite at about 700 F. To prevent too rapid reaction the exothermic material in the container may be covered with a thin layer of dry sand or some other insulating material. In order to avoid contamination of the metal after the mold is filled, it may be desirable, also, to cover the upper surface of the molten metal bounded by the inner wall 17 with a suitable insulating material, such as the layer of sand 25 shown in Fig. 4. A second covering of exothermic material may then be added with no ill effects.

The exothermic material used to fill the container may be of any suitable type which is now available. One type which has been found satisfactory contains (i.e. analyzes) 08% C, .45% MnO .087% P, .0ll% S, 3.75% SiO .l8% TiO 22.6% A1, 54.0% Fe O The analysis of another suitable exothermic material was as follows: .42% free C, 1.24% organic C, .19% MnO, .09% P 01% S, 48.7% SiO .04% N, .04% Cr O .l7% TiO 25.6% Al, 1.16% Cu, 6.90% Fe O .70% Fe, 1.6% A1 0, 1.19% G10, .76% MgO, 10.70% NaNO A third example of a satisfactory exothermic material had the following analysis: 27.80% SiO 22.70% A1 0 2.88% F3203, 24.53% metallic Al, 3.07% NaNO .to% metallic Mg, 7.34% MnO. The grades or types of exothermic material which have been found suitable generally contain amounts of aluminum and iron oxide as the principal reactants. Sodium nitrate is also used, and in some cases barium nitrate is used to replace sodium nitrate with the result that there is less smoke.

The exothermic temperatures have been found to reach approximately 4,300 F. Although there is some tendency for the container walls to break down under these extreme temperatures, the general effect is that the container walls are sufiiciently effective during the exothermic reaction to maintain the exothermic material out of direct contact with the molten metal, and prevent contamination of the ingots. After the reaction subsides, a white hot layer of residue is formed which keeps the metal in a molten state for an extended period. The time for complete solidification is extended by 20% over that when a conventional refractory hot top is used.

It has been found that exothermic and refractory materials, if not protected, will pick up moisture when stored for a period of time, and, therefore, previously when hot tops have been used with refractory liners or when exothermic material has been employed with such hot tops, the moisture in such materials has been released into the molten metal and the steam generated thereby has caused further damage to the ingot. With the employment of the container of this invention for the exothermic material, the molten metal is protected from the moisture which would normally be picked up by the exothermic materials, for in filling the container, it has been found that the exothermic material can be tamped into the container and thereafter allowed to dry so as to form a hard solid mass freed of a substantial part of its moisture. The exothermic material in the container is thereafter protected from picking up further moisture during the period it is stored in the container awaiting use in an ingot mold. One practical method of drying the exothermic material after it has been loaded into the container is by heating 4 gently until the material is substantially free of moisture and is formed into a hard solid mass.

Although it is preferred to have containers in the form shown which achieve good results without extending above the top of the mold, it is entirely within the scope of this invention to have the walls of the container extend above the level of the mold top, although it is desirable to have the container with the exothermic material extend a little way into the mold, eg at least two inches into the mold.

It has been found that by the use of the method and apparatus of this invention, it has been possible to increase the efiiciency in the pouring of ingots because the volume of metal needed to fill the area in the mold within the inner walls of the container is about one-half or less than that required in the present hot tops and that the use of the containers is much easier than the use of hot tops because the containers are lighter and easier to handle when placing on the mold, the molten metal is not contaminated by exothermic materials in direct contact with the metal, and, as noted above, the metal is protected from moisture from refractory or exothermic materials in contact with the metal. All these advantages have been achieved by the use of this invention and have resulted in a more efficient production of sound ingots with a reduction of the amount of scrapping of the upper end of the ingot.

In cases in which it is desirable to have the ingot extend above the mold so that it may be used as a tong hold for stripping of the ingot from the mold, a conventional refractory hot top may be used as an extension to the mold and the metal container filled with exothermic material may be placed in position inside the refractory hot top.

In accordance with the provisions of the patent statutes, I have herein described the principle of operation of the invention, together with the elements which I now consider the best embodiments thereof, but I desire to have it understood that the structure disclosed is only illustrative and the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combinations and relations described, some of these may be altered and modified without interfering with the more general results outlined.

Having thus described our invention, we claim:

In the combination of an ingot mold having an upwardly opening upright interior cavity into which molten steel is to be poured for casting an ingot, and a hot top structure for said mold comprising an annular sheet metal container having a central opening and arranged to be disposed for receiving the uppermost portion of the steel poured through said opening to fill the mold and the opening, said container being a unitary structure which has inner and outer walls of thin ferrous metal sheet and which provides a vertically extending annular recess between its inner and outer walls, to surround the central opening, the improvement which comprises said container having its outer wall shaped to fit closely within said cavity of the ingot mold, said container being positioned substantially Wholly within the mold, below and immediately adjacent the top of the mold, and said improvement further comprising, in combination, a mass of self-reactmg exothermic material contained in and held by said recess of the container and disposed in abutment with the inner wall around the central opening, in substantially encasing relation to said opening, said material being separated from the interior of the mold, at said opening, only by said thin ferrous metal of the container, said container being proportioned to hold, within its central opening, less than 10% of the total steel poured to fill the space which consists of said opening and the mold cavity below the container, and said container and said exothermic material being constructed and arranged to prolong, after pouring, the molten state of the poured steel ad jacent the top of the mold and to prevent contaminating 5 access of the reacted residue of the exothermic material 1,654,057 to the molten steel in the mold. 2,229,045 2,261,289 References Cited in the file of this patent 2,237,073

UNITED STATES PATENTS 5 1,192,617 Gathmann July 25, 1916 218,445 1,294,209 Walker Feb. 11, 1919 524,383 1,498,323 La Cour June 17, 1924 653,717 1,553,019 Bate Sept. 8, 1925 10 119,418

6 Smith Jan. 13, 1927 Cadwell Jan. 21, 1941 Rowe Nov. 4, 1941 Udy June 23, 1942 FOREIGN PATENTS Great Britain July 10, 1924 Great Britain Aug. 6, 1940 Great Britain May 23, 1951 Australia Jan. 5, 1945

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