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How Furnaces Are Charged gestive organs in the interior being conRunning parallel to the long row of tinually at work. Encircling the lower furnaces are the immense steel bins or outside portion of this tremendous test trestles filled with the ore, coke, and lime- tube, so to speak, is a large pipe punctstone. At the bottom of this structure ured at regular intervals by smaller ones are small electric cars which are kept busy which terminate in the interior of the transferring the desired ingredients—ore, furnace. As the powerful air-blast goes coke, and limestone—from the pockets rushing through these nostrils into the at the bottom of the bins to the skip car. body of this massive creature, where This being done, the skip, which operates every atom of it is caught and utilized upon an inclined track from the ground in some form or shape for the complito the top of the furnace, is conveyed to cated reaction therein, it sounds like the the top, where it automatically empties heavy, powerful breathing of some madits charge into the upper or receiving dened beast.
CLOSING THE IRON NOTCH AFTER RUNNING A BLAST FROM THE FURNACE. The large pipe circling the furnace is the bustle pipe, through which the hot blast is carried to the furnace.
bell. When filled, the bottom of this bell What Happens in a Blast Furnace is lowered and the material allowed to There are two distinctive series of op-' fall into a second and larger receiver. erations in the blast furnace—those When this has received its full quota, which accompany the charged materials consisting of several such loads and on their downward journey, and those known as a “charge,” its bottom is low- of the ascending gases. .. ered and the charge distributed uniform- As before stated, the superheated airly in the furnace over the top of the blast enters the lower portion of the furprevious charge. By these two bells or nace from all sides at a pressure of about bottoms, the top of the furnace is at all sixteen pounds to the square inch. Imtimes closed. The furnace is usually kept mediately upon its contact, the coke or filled within a few feet of its top.
coal, whichever is used as fuel, becomes But this is only a portion of the opera- combustible, the oxygen of the blast unittion—the food, as it were—the huge di- ing with the carbon of the fuel, forming
nace. The limestone is first changed into furnace. Owing to their lower specific caustic lime, which unites with the gravity, the slags float on top of the iron, alumina and silica of the ore and ash of protecting the same from the influence of the fuel, with the result of a double the blast. silicate of lime and alumina. This is very fusible and does not mix with the iron.
What Becomes of the Gas ? The incombustible and solid matters The gases accumulating from this conare so mixed and proportioned with the glomerate mass of liquid, semi-liquid, and combustible and fusible materials that the heated substance, rise to the top. Not
finding an escape through the charging Cup Moulds Sometimes Used bells, they dart down the two or more When wanted for basic purposes and “downcomers" which are provided for free from sand, another method is emthis purpose. Here they are led through a ployed. Instead of permitting the iron box, where the cinders and other solid to run into the sand moulds, it is run matters are extracted. A portion of the through the channels into specially congases is now carried through pipes to structed ladles or vessels which operate feed the boilers, while another portion is upon wheels. These have a capacity of utilized in the heating of the stoves. 18,000 pounds each ; five to six are usu
These stoves, as before mentioned, are ally filled from each blast or cast. As large, cylindrical structures whose in- filled, they are drawn to the casting house, teriors are masses of fire bộick. These where they are tilted in such manner as to bricks are so arranged as to allow the permit the molten metal to run into an greatest amount of surface to be exposed. In this manner they are thoroughly heated. Each furnace has a set of such stoves, some of which are always being heated, while others are giving their heat to the blast which is driven through them prior to entering the blast furnace proper. At intervals these stoves are changed, the cold ones heated and the hot ones employed for heating. This method of utilizing the waste gases is a comparatively new invention, but one which has almost revolutionized the iron industry.
How Hot Iron is Cast Formerly there was but one method of casting pig iron ; but, because of the rapid advance in the uses to which this material is adapted, several methods are now employed. The ultimate results of these methods are of a physical rather than a chemical nature. In any case, however, the iron is first tapped through an opening near the bottom of the furnace, at periods of four hours' duration. Leading from this opening is a long channel in the
FILLING THE SKIP CAR WITH THE NECESSARY MATERIAL sand, through which flows the white,
TO MAKE A CHARGE. glittering iron.
If it is to be cast in the form of sand endless chain of cups. These cups are pig, the metal runs into a long channel about two feet long and eight inches wide in the sand, with smaller ones running at at the base, and are attached to an endriglit angles to both sides. These are less chain that rests upon a track. By called “sows." Flowing from the sows, means of an engine or motor, the chain the iron is fed into smaller moulds, about is revolved, the cups passing through a three feet long and four inches wide. long tank of water, at the end of which When solidified, these "pigs," as they are is an incline, up which the chain bearing termed, are broken from the sows and the cups passes. When it reaches an eleloaded into cars, ready for shipment. Iron vation of about ten feet, the chain passes thus cast has an accumulation of ad- over two gear wheels on its way back. hesive sand upon its surface. It is not The cups turn up-side-down, throwing extensively used in any processes where their now solid contents into a car besand or silica is a detriment.
During recent years the expense of slag, coming in contact with the water, casting has been greatly lessened by the solidifies in the form of shot or sand. invention or practice of using the iron This is continually being lifted out by direct in its molten condition. It is trans- large electric scoops and loaded into cars. ferred in ladles direct from the blast fur In this form it is utilized either for cenace to the steel furnaces, thus avoiding ment or ballast. If ladles are used, the a second melting in the latter operation. molten slag is allowed to flow into several
specially built ladies, which, when filled, What Happens to the Slag
are carried away and dumped into raThe slag is run off at irregular inter- vines and hollows. vals, in a manner similar to the iron, but There are many grades of iron, difthrough an opening above the iron line. ferent only as to their chemical composiThis avoids any possible waste of iron. tion. The most common of these are: Channels are built in the sand to lead the Foundry, gray forge, mottled, white, slag from the furnaces to either a gran- standard Bessemer, basic, and malleable ulating pit or to the ladles. In the Bessemer. The foundry irons are subformer case it falls into a large pit or divided into Nos. 1, 2, and 3, according well containing water. The hot, liquid to the percentage of silicon.
Analysis of Pig Irons The following table gives a rough analysis of the several grades of pig iron: GRADE
SULPHUR PHOSPHORUS MANGANESE No. 1 Foundry....... 2.50% to 3.00% .03% and under .40% to .80% 30% to .60% No. 2 Foundry........
2.00% to 2.50% .04% and under .40% to 80% .30% to .60% No. 3 Foundry....... 1.75% to 2.25% .05% and under .40% to .80% 30% to .60% Gray Forge........ 1.25% to 1.75% .07% and under 40% to 90%
variable Mottled ............. about 1.00% .10% and under variable
variable White .............. about 1.00% .15% and under variable Standard Bessemer... 1.00% to 2.00% .05% and under .10% to 20% Basic..
.... 1.00% and under .05% and under 50% to 1.00% Malleable Bessemer.. 1.25% and under .05% and under .15% and under