US2250009A - Exothermic insulating compound - Google Patents

Description

Patented July 22, 1941 UNITED STATES PATENT OFFICE nxornammo INSULATING COMPOUND John Leroy Coble, Aliquippa, Pa-

No Drawing.

5 Claims.

- from the metal and which becomes exothermic to aid in such retardation.

In the present practice in common use in the art such insulating materials as lime, sand and clay; and sometimes such combustible substances as straw, cork, coke and the like, have been employed for this purpose, but the results have not been entirely satisfactory because objectionable piping and cavitation of the ingot or casting still occurs, necessitating the cropping off of an excessive percentage of the cast product to eliminate defects. I

The object which I have in view is the provision of a new and improved compound which, when applied to the surface of the molten metal in the hot top of the mold will blanket the molten metal and retard the escape of heat and will also by its exothermic action retainthe metal in the hot top in such a fluid state that itwill readily flow into the cavity formed by shrinkage and thus prevent or reduce piping to a minimum, thereby limiting the metal which must be cropped from the ingot tothat portion thereof which is retained in the hot top after the ingot hardens.

My improved compound is a mixture of a noncombustible insulating material and a fuel, both in ground or granular form. For the insulating material I use either granulated blast furnace slag or-exfoliated vermiculite material, while for the combustible content of the compound I use ground coke or coke breeze, or gas-producer flue dust.

Thus I have used in the commercial casting of steel ingots the insulating compound as follows, the percentages being given by weight.

Example No. 1

Percent Ground coke or coke breeze 60 Granulated blast furnace slag 40 Example No. 2

Percent Ground coke or coke breeze 85 Exfoliated vermiculite granules 15 Example No. 3

' Percent Ground coke 25 to 40 Flue dust 30 to 25 Granulated blast furnace slag 45 to 35 Application March 19, 1940, Serial No. 324,817

Example No. 4

Percent Flue dust 50 5 Granulated blast furnace slag 50 by practice.

The granulated slag above referred to is produced by directing a high pressure stream of water into the molten slag as it flowed from the runner of the blast furnace.

The amount of compound used is determined Usually from /g to 1 /2 pounds of the compound per ton of molten metal is sufiicient.

The above compound may be varied in accordance with the materials available but in case the carbon content of the insulating mixture material is reduced below 30% a small quantity of ferro-silicon or some other deoxidizing agent should be added to the compound to compensate for the deficiency in carbon.

To realize the full advantages of my improved compound a close check must be made of the raw materials. First, they must be free from excessive moisture, and after the materials are intermixed to form the compound, they must be stored in a closed container until used, if the maximum insulating value is to be obtained. The correct amount of the compound should be employed and it should be applied to the top surface of the molten metal in the mold immediately after the ingot or casting is teened and the stream of molten metal is shut 011'.

Due to the lightness of my improved compound it spreads easily over the surface of the molten metal in a uniform layer.

When applied by the above procedure there is no bridging" of the material of thecompound above the steel in the hot top of the mold, and the steel as it hardens will drop parallel with the walls of the hot top. This is especially true where the steel is from .25 to .40 carbon with .75 to 1.40 manganese. In the case of the lower carbon steel the drop is not so pronounced.

In the case of a big-end-down ingot mold having cross sectional dimensions of 24"x24" fitted with a hot top, with the use of my compound, approximately 750 cubic inches or 192 pounds of molten metal may be displaced from the hot top in from twenty to thirty minutes in the case of .25 to .40 carbon steel.

Due to the formation of a slag which floats on the top of the metal there is no pick-up of carbon from the molten metal.

This remarkable displacement of the metal is due to the fact that with the use of my compound the metal from the hot top flows downwardly into the mold and fills up any 'cavita on which may be produced by the outward 1 shrinkage of the metal in cooling. With the use of my material, piping or cavitation caused by shrinkage of the molten, metal in cooling is practically eliminated, and the metal which must be cropped ,i'rom the ingot before the same is rolled is limited to that which remains in the not top after the solidification of the metal is completed. Thus a very substantial saving in metalisrealized. p

Also owing to the fact that there is no tendency of the compound to bridge or form a selfsustaining layer over the top of the metal in the compound, there is no formation oil a cavity in the metal in the hot top or in the upper end of the ing'ot as is characteristic of ingots cast with the use of sand or lime as an insulating material.

Another" advantage of my invention is the low cost of the material compared to the cost of other compounds hitherto used for this same purpose.

As the carbonaceous material I prefer to use coke breeze or flue dust. The last named is a carbonaceous material which is deposited in the fiues of a gas-producer and which is composed largely of carbon.

The analysis of mately as follows,

these materials is approxithe amounts being given by The blast furnace slag which I may use in ground form is the incombustible material which may be basic furnace slag or Bessemer blast furnace slag, and the analysis of these by weight is approximately as follows:

s10, Also: CaO MgO Basic furnace slag 36 48 3 Bessemer blast iurnace slag 38 9 i 47 5 I claim: lrA loose exothermic insulating compound to granules.

be spread over the'surface of molten cast steel for preventing piping and cavitation in the formation of ingots and other castings, which comprises an intimate -admixture of from 30% to 65% by weight 6: a finely divided carbon combustible and the balance finely divided blast iuri nace slag. composition consisting essentially *0! the oxides of silicon, aluminum, calcium and magnesium.

2. A loose exothermic insulating compound to e spread overthe surface of molten cast steel for preventing piping and cavitation in the formation or ingots and other castings, which comprises an intimate admixture by weight of approximately or a finely divided carbon combustible and 40% off finely divided blast furnace slag.

3. A loose exothermic insulating compound to be spread over the surface of molten cast steel for preventing piping and cavitation in the formation of ingots and other castings, which comprises an intimate admixture by weight of approximately from 55% to of a finely divided carbon combustible and of from 45% to 35% of finely divided blast furnace slag composition consisting essentially of the oxides of silicon, aluminum, calcium and magnesium;

4. A loose exothermic insulating compound to be spread over the surface of molten cast steel for preventing piping and cavitation in the formation of ingots and other castings, which comprises an intimate admixture by weight of approximately of a finely divided carbon combustible and 15% of exfoliated vermiculite granules.

5. A loose exothermic insulating compound to be spread over the surface of molten cast steel for preventing piping and cavitation in the formation or ingots and other castings, which comprises an intimate admixture of from 30% to 85% by weight of a finely divided'carbon combustib'le and the balance at least one insulating material of a group consisting oi'a finely divided blast furnace slag and exfoliated vermiculite JormnERoY COBLE.