THE BLAST FURNACE
 
              The purpose for which the Blast Furnace is used is to reduce, or
         deoxidize, and smelt the iron ore (iron oxide), converting it from an oxide to a
         metallic state.
 
              While the art of smelting iron ores in a blast furnace has been known
         for centuries, very little was generally understood of the phenomena until about
         the middle of the Nineteenth Century, when Sir Lowthian Bell published his
         first treatise in Bngland on the chemical actions, and reactions, that take place
         inside the blast furnace.  Much has since been learned, but Bell's fundamental
         principles continue undisputed.  Bell, a learned metallurgist and chemist,
         amidst a very busy and active life, found time to determine, by reasoning and
         calculating, these phenomena.
 
              The process of smelting iron in the blast furnace consists essentially of
         charging a mixture of fuel, ore and flux into the top of the furnace, and simul-
         taneously blowing in a current of heated atmospheric air at the bottom.  The
         air burns the fuel, forming heat for the chemical reactions and for melting the
         products; the gases formed by this combustion remove the oxygen from the ore,
         thereby reducing it to metallic form; the flux renders fluid the earthy materials.
         The gaseous products of the operation pass out at the top of the furnace, while
         the liquid products, cast iron and slag, are tapped at the bottom.  The escaping
         gases are combustible, and therefore are conducted through pipes to boilers and
         stoves where they perform the useful services of heating the blast and generating
         steam for operating the engines.
 
              It is evident, therefore, that several factors enter into the composition
         of a complete smelting unit.  The central feature is the furnace with its hoists
         and skips for the handling of charges, and its ladles and pig machines for hand-
         ling the products.  Quite as essential are the blowing engines which drive the
         blast to the furnace, through a series of hot blast stoves, which heat the blast
         on its way.  Not less important are the boiler plants and the pumps which
         furnish the power to drive the blowing engines and supply the vast quantities of
         water needed for cooling purposes.
 
              The furnace proper is a large steel stack, about 80 feet high, lined inside
         with high temperature, refractory brick.  It is comprised of three distinct parts,
         each having a different function.  The shaft, or upper part of the furnace, has
         an inside diameter of 13 feet at the top, gradually increasing to 17 feet where it
         connects to the bosh, about two-thirds of the way down.  The bosh, having
         an inside diameter of 17 feet at the top, where it connects to the bottom of the
         shaft, gradually decreases to a diameter of 13 feet at its bottom, where it connects
         to the top of the hearth.  The hearth has a diameter of 13 feet straight down to
         its bottom, which is the bottom of the furnace.

              In order to protect and prolong the life of the brick lining, hollow
         bronze cooling plates are inserted at intervals, through which water is contin-
         ually circulated.
 
              The ratio of ore, and its accompanying flux, to the fuel of a furnace
         charge, is generally termed the "burden" of the furnace.  The task of deter-
         mining the quantity of each, which is best suited to furnace conditions, is desig-
         nated as "burdening the furnace."  The successful running of the furnace
         probably depends more upon burdening than upon any other single factor in
         its management.  In the early days of the industry, before the constant applica-
         tion of chemical analysis to the materials used, burdening was a combination
         of previous experience and guesswork.  If any raw materials from an unfa-
         miliar source had to be used, the treatment required had to be guessed, until it
         could be determined by experience. With the application of analytical methods,
         however, it became possible to predict, with tolerable accuracy, the requirements
         of any materials from their chemical composition.
 
              The raw materials are put into the furnace in alternate layers of coke,
         and a mixture of iron ore, limestone, and sometimes manganese bearing material.
         These are called "charges," and take up a space in the furnace from four feet
         to six feet in depth.  The furnace is kept full, to within a few feet of the top,
         at all times.
 
              The blast of air, which has been preheated to about 1,400 degrees Fah-
         renheit by the stoves, is forced into the furnace through pipes, connected to
         short, hollow, bronze, water cooled tubes, called "tuyeres," having an inside
         diameter of about 5 inches  There are eight of these "tuyeres" evenly spaced
         around the upper part of the hearth, and just below the bottom of the bosh.
 
              The carbon, liberated by the burning of the coke at the bottom of the
         furnace, unites with the oxygen of the incoming blast of air, forming large
         quantities of gaseous compounds, including carbon monoxide (CO).  This gas
         has a great affinity for oxygen.  Therefore, as it passes up through the raw
         materials in the shaft of the furnace, it unites with the oxygen in the iron ore,
         reducing the ore to a metallic state, and passes out through the top of the
         furnace as carbon dioxide (C0₂). There is always more than enough carbon
         monoxide present to completely reduce the iron ore.  The remainder is burned
         under the boilers to make steam and in the stoves to preheat the blast of air
 
              By the time the materials reach the top of the bosh, the iron ore is all
         reduced to a metallic state, and the carbon dioxide (C0₂) has been driven out
         of the limestone, changing it to lime (CAO.).  The iron and slag forming
         materials begin to melt at this point, and trickle in streams down through the
         voids of the coke bed into the hearth.  The molten iron, being heavier, goes to
         the bottom, and the molten slag, being lighter, rests on top of the iron.  The
         slag is drawn from the furnace through the cinder notch at various intervals.
         This is called "flushing."  The iron is drawn from the furnace through the
         iron notch, periodically, from four to six times in 24 hours.  This is called
         "casting."
 
              The slag drawn from the furnace goes to large, standard gauge, ladle
         cars, and is sent directly to the slag dump.  The quantity of iron drawn from
         the furnace, at cast time, will vary from 35 tons to 60 tons, depending upon
         how fast the furnace is driven, and it goes directly to a large 70-ton capacity
         ladle, which is lined with high temperature refractory brick.
 
              At the end of the cast, the tapping hole, or iron notch, is plugged with
         fire clay, by means of a steam operated cylinder, known as the "mud-gun," and
         the blast again put on the furnace.  Immediately after this has been done, the
         molten iron is poured from the ladle into the pig casting machine, a continuous
         strand of cast iron moulds, mounted on wheels and traveling on an inclined track.
         It is sprayed with a thin stream of hot water and steam, so that by the time
         it reaches the discharge end of the machine, is is solidified into small blocks of
         iron, weighing about 65 pounds each, called "pigs."  It is then discharged
         directly into the railroad car, from where it is sent either to the storage yard or
         to market.
 
              The ingredients from which Chateaugay iron is made are coke, lime-
         stone, Chateaugay sintered ore and, when making manganese bearing iron, man-
         ganese residuum, a product from ferro-manganese furnaces, is added.  All of
         these materials contain certain elements that must be eliminated from the iron
         in the process of manufacture.  It is, therefore, necessary to know the exact
         chemical composition of each ingredient before it is put into the furnace.  This
         is learned by sampling and analyzing the materials daily.  When any appreci-
         able change in chemical composition of any of the materials is discovered, the
         burden must be changed accordingly.
 
              The principal detrimental elements that high grade pig iron should be
         kept free of are sulphur, phosphorus, chromium, copper and arsenic.  The
         Chateaugay iron is entirely free from chromium, copper and arsenic, because
         none of the raw materials used in its manufacture contain any of these elements.
         Sulphur enters the furnace in the coke, and is nearly all eliminated in the slag.
         Phosphorus enters the furnace in slight amounts in the ore and in the coke.
         It has a greater affinity for molten iron than for the slag and, therefore, all of
         the phosphorus that goes into the furnace enters the iron.  The Chateaugay
         iron is very low in phosphorus, because the ore from which it is made is prac-
         tically free from that element.  This is also true of the coke and limestone used.
 
              There are at least 35 different and distinct varieties of Chateaugay iron
         made and sold to the trade.  All of these grades are amazingly free from
         impurities, and are distinguished by the percentages of different metalloids con-
         tained therein, such as silicon, carbon and manganese.
flow102.jpg

                    When making the various kinds of iron, the furnaceman has at his
                command three variables, by which he must achieve the desired results.  They
                are the heat, burden composition and slag composition.  With sufficient heat,
                properly composed burdens and properly composed slags, a wide range of
                products may be obtained from identical materials.  The proper amount of
                heat in the furnace is that which will maintain the least temperature necessary
                to perform the work desired; any excess is waste.  The temperature which is
                necessary to obtain given results depends upon the product desired, and is insep-
                arably linked with the slag composition.  Generally speaking, the slag is the
                substance that requires the highest temperature for its proper function and
                disposal and, when that temperature has been attained, it is ample for all other
                purposes.

                     The slag serves a two fold purpose in the furnace.  It is the means by
                which the temperature of the hearth is controlled, and also by which the sulphur
                is kept out of the iron.  If it is too fluid, it will flow down through the voids
                of the coke bed rapidly, without absorbing and carrying sufficient heat down
                into the hearth.  If it is too viscous, it will not flow through the voids, but will
                clog up the furnace, prevent the free passage of the upward flow of the gases and
                interfere with the regular movement of the stock in the furnace, making it
                necessary to check, or take the blast off entirely, at frequent intervals until the
                condition has been corrected.
                     It will, therefore, be readily seen that it is highly important to arrange
                for the composition of a slag that will not be too fluid nor too viscous, but
                will have a consistency which will allow it to flow freely and slowly through
                the voids of the coke bed, in order to function properly.
 
                     In addition to the above, it is highly important that the chemical com-
                position of the slag be such that it will have a greater attraction for the sulphur
                than the iron, the slag being the only positive means of eliminating the
                sulphur, practically all of which enters the blast furnace in the coke.  Under
                favorable conditions, the sulphur will unite with the lime in the slag, forming
                calcium sulphide.  If conditions are unfavorable,. it will unite with the iron,
                forming ferrous-sulphide and spoiling the iron.
 
                     As previously stated, the phosphorus content of the pig iron is practi-
                cally independent of furnace manipulation, but depends almost entirely upon the
                nature of the materials used.  Probably never less than 90 per cent of the phos-
                phorus present enters the iron, and more often it is nearer 100 per cent.  There-
                fore, in order that this element be kept out of the iron, it must not enter the
                furnace.
 
                     The quantity of carbon which enters the pig iron is independent of the
                furnace burden.  It is present in two forms: graphitic and combined.  The
                sum of the two is known as "Total Carbon," which ranges from 3.00% to
                4.50% in the pig iron.  Carbon comes from the coke, and is deposited in the
                iron in various amounts, depending upon the temperature of the hearth and the
                other metalloids in the iron.
 
              Silicon in the iron varies from 0.50 % to 4.50 %, depending almost
         entirely upon the manipulation of the furnace.  It is produced by reducing, or
         deoxidizing, the silica under high temperature.  It has a very strong affinity
         for molten iron.  Due to its importance, it is the one element, more than any
         other, that is responsible for the grading of the iron into so many varieties.
 
              Manganese in the iron varies in percentages from 0.00 % to 2.50 %.
         It has little or no effect in amounts under 0.15 %.  Chateaugay iron is made
         with or without manganese.  About 75 % of the total manganese that enters
         the furnace goes into the iron.  Some of it goes out with the slag as an oxide,
         and the remainder is lost by volatilization.
 
              The Chateaugay iron is made entirely from Chateaugay ore.  No for-
         eign scrap of any kind is put into the furnace.  In other words, it is an all-ore
         pig iron and, without a doubt, the purest to be found anywhere.
 
              In connection with the blast furnace, there is a small iron foundry, used
         for making iron castings.  The molten metal used comes directly from the blast
         furnace and is run into small ladles for pouring the castings.
 
              The pig iron, after it is made into pigs, is all carefully weighed, and
         either goes directly to market or to the storage yard, where it is piled separately
         according to its chemical composition.  When iron is taken out of storage for
         shipment to market, the railroad car is first thoroughly cleaned, and weighed
         light, and is again carefully weighed after it is loaded.

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