US2843898A - Hot top - Google Patents

Description

R. W. CARTER July 22, 1958 NVENTR.' ROBERT u'. CAR TER, WM/7M@ lHEL. E-

HOT TOP Filed Aug. 5, 1956 TTS-1 his Attorney.

United states Patent o Hor ToP Robert W. Carter, Library, Pa., assignor to United States This invention relates to a hot top and is directed primarily to that type of hot top which has a cast steel shell lined with refractory. The hot tops of this type in common use use insulating refractory which is provided With a protective lining of a water mixed parting compound applied to a minimum thickness of 1/2 in. Such hot tops and linings are shown in Urmetz Patent No. 2,046,043, dated June 30, 1936, and Peterson Patent No. 2,678,481, dated May 18, 1954. After the parting compound has dried the hot top is placed on the ingot mold and the molten steel poured therein. Before the hot top can be used again a new lining of the parting compound must be applied and dried. This operation is laborious, time-consuming and expensive. The average life of the hot top before relining with insulating material is approximately 35 pours. The reason for the short number of pours is that the insulating material is eroded by the molten metal in spite of the slight protection of the parting compound.

It is an object of my invention to provide an improved hot top or a protective lining therefor wherein the life of the hot top before relining is greatly increased.

Another object is to provide such a hot top which enables the volume of molten metal contained therein to be reduced with a corresponding increased yield from the ingot.

These and other objects will be more apparent after referring to the following specification and attached drawings, in which:

Figure 1 is a vertical section through the preferred embodiment of my invention;

Figure 2 is a sectional view taken on the line II-II of Figure l;

Figure 3 is a View of the mold of Figure l showing an intermediate stage in its manufacture; and

Figure 4 is a view similar to Figure 1 showing a modification of my invention.

Referring more particularly to the drawings, the reference numeral 2 indicates a tubular shell preferably made of cast steel. A sand ring 4 is attached to the bottom of the shell 2. Both the shell 2 and sand ring 4 are standard in this type of hot top as shown by the above mentioned patents and no invention is claimed in so far as these two parts are concerned. Special types of sand rings are shown in Charman Patents Nos. 1,956,894 and 1,956,895, both dated May 1, 1934. A lining of insulation is provided on the inner surface of the shell.` This lining 6 may be an insulating block of a commercial type having a base of vermiculite, diatomaceous earth, mineral wood or silicate-gel. The block may be molded or pressed from these materials or combinations thereof and may be burned or unburned. They have a high insulating value, the coefficient of thermal conductivity K being not more than 1.2 B., t. u./sq. ft./F./in. thick/hr. Insulating tire brick may also be used these being mixtures of clay and saw dust or other combustible which burns out leaving a porous clay brick. The insulating value is less than for block, K generally being between 2 and 3.

The blocks will stand temperatures between 1200-2000 F. and the insulating brick will stand temperatures of between 1600 and 3000 F. A high temperature air setting cement coating 8 is applied over the lining 6. This cement is a clay or clay/alumina base mortar containing sodium silicate or other air setting bonds to provide cold` setting or air setting properties. A castable refractory lining 10 is placed on top of the cement coating 8. This is Ia calcined lireclay or fireclay grog/alumina product which when tempered with water will develop structural strength by reason of a hydraulic set as provided by calcium aluminate cements such as that sold under the trademark Lumnite. A thin layer of parting compound 12 is arranged on the refractory lining 10. This parting compound is an air setting sand mixture generally containing some carbonaceous material.

In making the hot top the inner surface of the shell 2 is lined with insulating lire brick or insulating block 6 and a thin layer approximately 1A; in. thick of a high temperature air setting cement is applied thereto.. A form F is then placed on the mold in any suitable manner as shown in Figure 3. The high temperature castable refractory lining 10 is placed between the mold F and the cement lining 6. The cement acts: as a bond between the layers 6 and 10 and also as a seal to prevent water from the layer 10 getting into the insulating layer 6. It will be noted that the inner surface of the coating 12 is tapered for a purpose which will appear later. The surface of the form F is well oiled to facilitate removal of the form. One or two hours after the refractory castable lining has been poured a plurality of vent holes 14,

twelve of which are shown7 are pierced in the: top portion of the castable refractory lining to permit moisture to escape during drying. The form F is removed eight hours yafter pouring of the refractory, this being facilitated by the taper in the lining 12. After the form is removed the hot top is permitted to air set for about four hours after which it is heated to remove the moisture.

When the hot top is to be used on an ingot mold the sand ring 4, which is a molded ring pressed with an air setting bonded material and dried, is placed on the mold in the usual manner .and the parting compound 12 having a thickness of about la in. is put in place and dried. The coating of parting compound is destroyed during the cast but it is only necessary to replace the sand seal 4 and coating 12 before the hot top is ready for another pour. The life of the lining proper is greatly increased over that of the old type and in many instances over pours have been made in one hot top before the lining proper is replaced. Since the layer of parting compound is much thinner than in the former hot tops the time required to dry the same is much less.. The castable refractory lining 10 protects the insulating layer 6, thus permitting the longer life. The insulating material prevents loss of heat so that the volume of molten steel in the hot top can be reduced. While it is preferred to cast the castable refractory lining 10 in place it is possible to pre-cast the refractory into block or bricks and lay them in place.

Figure 4 shows another modication of my hot top which has some of the advantages of my preferred embodiment. In this embodiment a monolithic lining 16 of a castable refractory of the type described above is cast on the inner surface of the tubular shell 2 and a thin coating 18 of parting compound corresponding to the coating 12 is placed thereon.

While two embodiments of my invention have been shown and described it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

I claim:

l. A hot top comprising a tubular shell, a lining of insulation on the inner surface of said shell, a coating of high temperature air setting moisture resistant cement on said insulation, and a high temperature castable refractory monolithic lining on said coating.

2. A hot top comprising a tubular shell, a lining of insnlotion on the inner surface of said shell, a coating of mh temperature air setting moisture resistant cement on said insulation, a high temperature castable refractory monolithic lining on said cement, and a thin coating of a parting compound on said refractory lining.

3. A hot tolga` comprising a tubular shell, a lining of insulation on the inner surface of said shell, a high temperature moisture resistant seal coating on said insulation, and a high temperature castable refractory monolithic lining on said coating.

References Cited in the lle of this patent UNITED STATES PATENTS 710,588 Knox Oct. 7, 1902 1,837,146 Brooks Dec. 15, 1931 10 1,982,490 Williams et al. Nov. 27, 1934 2,293,089 Wajner -1, Aug, 18, 1942 FOREIGN PATENTS 708,599 Great Britain May 5, 1954

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