US437109A - Process of remelting iron in cupola-furnaces - Google Patents

Description

(No Model.)

Patented Sept. 28, 1890.

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UNITED STATES PATENT OFFICE.

HENRY J. GRAF, OF ST. LOUIS, MISSOURI.

PROCESS OF REMELTING IRQN IN CUPOLA-FURNACES.

SPECIFICATION forming part of Letters Patent No. 437,109, dated September 23, 1890.

Application filed February 25, 1890. Serial No. S LL'YOB. (No specimens.)

To all whom it may concern.-

Be it known that I, HENRY J. GRAF, of St. Louis, in the State of Missouri, have invented certain new and useful Improvements in the Process of Remelting Iron in Cupola-Furnaces, of which the following is a full, clear, and exact description, reference being bad to the accompanying drawings, forming a part hereof.

Heretofore in remelting iron in a cupolafurnace for the production of castings the air that is blown in has come in contact with the liquid metal and the carbon-thereof, and the metal is decarbonized to a considerable extent, and the oxide is correspondingly increased in quantity. The iron having been left too long in such semi-fluid condition subject to the action of the blast, the oxygen has united with the carbon of the iron and converted a considerable portion of it into steel. The iron has therefore lost a corresponding percentage of graphitic carbon, retaining only combined carbon. Iron melted under such conditions does so very slowly, and drops down into the semi-fluid mass at the bottom of the cupola and deteriorates the quality of same, causing hard spots in the castings. Furthermore, such iron having lost uncom bined carbon will be less fluid, and the result will be imperfect castings.

The objects of my invention may be briefly stated as follows: To increase the outflow of carbonic acid; to increase the temperature of the furnace, using less fuel and blastpressure than are at present necessary; to retain great heat at the bed and permit but little to escape at top of furnace or charging door; to decrease the quantity of coke now used in the bed and between charges 5 to provide a material which shall act as a flux; to prevent decarbonization during the melting process, and to improve the quality of lowgrade iron, such as scrap, &c.

To these ends my invention consists in charging the furnace with scrap or pig iron, ignited coke, and gas-carbon in alternate layers, whereby the iron is segregated from the direct action of the mass of the blast and caused to receive a diffused blast, and whereby the iron is kept from a long continuation of that blast, thus preventing a great loss of carbon, and placing the iron in such a position that when melted it will reach and take up a larger proportion of graphitic carbon. This segregation and location of the iron is effected by the interposition of the gas-carbon beneath the iron and between it and the fuel, as will be hereinafter more fully described and claimed.

1 will now proceed to describe more specifically the manner of carrying out my invention, and for facility in doing the same I have illustrated apparatus suitable therefor.

Inthe drawings, Figure 1 is a vertical sec tion of an ordinary cupola-furnace, and Fig. 2 is a perspective view of a detached and enlarged particle of gas-retort carbon made use of in carrying out the invention.

Like letters refer to like parts in .the two figures.

A indicates the outer shell of an ordinary cupola, the same being provided with a suitable lining upon its interior, and being mounted upon suitable iron columns, (or a base of masonry,) such as B. This shell is provided with a drop-bottom O, and in use should also have a sand-bed D. Tuyeres E, slag-hole F, and tap-hole H are also provided in the usual 7 manner, as is also a straight open-topped stack and a charging-opening I.

The direct or natural draft is used in starting the fire, as is usual in these cases.

My improved method of charging the furnace and the material employed therein is as follows: I first place a charge of ordinary coke J on the bottom of the furnace, which forms a base or stratum upon which the next adjacent stratum is adapted to rest. This bed-stratum is then ignited and the blast is turned on. Then a thinner stratum of gas-1e tort carbon (commonlyknown as suchin other usages) K is placed upon the coke-stratum J, said gas-retort carbon having previouslybeen broken up to about what is known in the coal trade as egg size. After the charge of gasretort carbon has been thrown into the furnace it is evenly distributed over the cokestratum, or it may be distributed properly during the process of throwing it in, thus giving it the best opportunity to ignite.

L is a charge of iron, in the form of pig, scrap, or otherwise, scrap being preferred, as

its cost is low and its quality will beimproved suflicient for use in high-grade castings.

M is a small charge of coke.

N is another stratum of gas-retort carbon, and O is another charge of iron, and so on until the required amount of iron is melted.

In carrying out the usual process of treating iron in cupola'furnaces the air that is blown into the furnace contains aqueous Vapors, and by their action upon the liquid metal and carbon the former becomes deearbonized and liberates the latter in the form of a gas, while if the semi-fluid iron is subjected to the blast and cold air for too great a length of time it falls down into the molten metal and the latter deteriorates. These troubles I overcome by using the aforesaid carbon and by using the same amount of blast that is commonly used until the carbon is ignited, when I decrease the blast about fifty per cent. By these means carbonic-acid gas is not driven out of the stack of the furnace in such great quantities has been previously the ease, and the amount of aqueous Vapors passing through the cupola is decreased. As the temperature is thus increased the iron is rapidly fused, it being left for a short time only subjected to the cold air, and as the carbon is melted it is precipitated into the iron, thus leaving it wholly uncombined and in a graphitic state.

By my process above described fifty per cent. less fuel (coke) is required between charges of iron during the melting operation, and I have found that fifty per cent. less blast is required to accomplish the results aforesaid, and therefore heat will not be thrown out of the charging-opening and top of furnace, asheretofore. About two percent. of gas-retort carbon to one hundred per cent. of good scrap or pig is required.

I am aware that previous to my invention carbon has been blown through molten iron, (the carbon being in the form of a powder and being introduced within the cupola through the tuyeres,) and that iron has been melted by the use of carbon alone, and I do not therefore desire to claim such a process; but

'What I do claim, and desire to secure by Letters Patent, is-

1. The herein-described process for remelting and refining iron in cupola-furnaces, which consists in subjecting alternate layers of scrap or pig iron, ignited coke, and gas carbon to a blast, as and for the purpose described.

2. The hereinbefore-described process of treating iron in cupola-furnaces, which consists, first, in charging the said iron in layers and alternately with a layer of gas-carbon and a layerof coke; second, blowing air therethrough until the carbon is ignited, and, third, reducing the amount of the said air-blast, as described.

In testimony whereof Iaflix mysignature in presence of two witnesses.

HENRY J. GRAF.

\Vitnesses:

JNo. (l. IIIonoN, U. K. JONES.

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