Pud′dling-fur′nace.
（
Metallurgy.) One in which
pig-iron, broken into pieces and mixed with
hammer-slag, cinder, ore, according to circumstances, is melted and continuously stirred for a considerable time while boiling, in order to expose it thoroughly to the action of the current of air passing through the furnace, so as to effect the chemical changes required for the separation and removal of the impurities originally combined with the iron.
The metal has then to be balled up into separate masses of about one hundred and twenty pounds each for the shingling hammer; and the whole process extends over about an hour, from the time of melting the
pig-iron for each heat, of which six are worked in the day.
The process involves very laborious and longcontinued hand-labor, and the current of air passing through the furnace has to be regulated and changed as the process advances.
Fig. 3993 gives an idea of the general appearance of the exterior of the furnace.
The furnace-door is by the man in the foreground, who is holding the handle of the
ball-trolley to catch the
ball or
loup, which the furnace-man is just taking out of the iron chamber.
A third man lifts the door by means of the lever
Fig. 3994 shows a puddling-furnace of usual construction.
The furnace-door is at
L; D, the door of the iron-chamber;
K, the neck;
M, the stack.
The iron boshes stand on pillars, and their exteriors are cooled by water introduced by tubes The
stack M also stands on pillars, so that it is not affected by the tearing down of the
neck.
Fig. 3995 shows two forms of puddling-furnaces; a singlechambered and a double-chambered furnace.
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1817]
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Puddling-furnace. |
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Puddling-furnace. |
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Puddling-furnaces. |
In
Fig. 3995,
A, —
| a, fire-chamber. | h, stack. |
| b, iron-chamber. | i, velvet-tree. |
| c, hearth. | k, grate. |
| d, stock-hole. | l, roof. |
| e, throat. | m, tap-hole. |
| f, neck. | n, stopper-hole. |
| g, bridge. |
In
Fig. 3995,
B, —
| a, first fire-chamber. | d, water-back. |
| a′, second fire-chamber. | f, pipe to supply water-boshes g. |
| b, metal-chamber. |
| c, bridge. |
Fig. 3996 shows the plan-view of the fire-chamber, ironcham-ber, neck, and stack.
The water-jacket is open above, giving free exit to steam, and the separate sections are connected by tubular bolts, allowing passage of water.
The bridges contain water, and have ascending and descending steam and water pipes.
The puddling-furnace was invented by an iron-master of the name of
Henry Cort, about the year 1780, the bed of whose furnace was made of sand, consequently the carburet was refined, many of its impurities, especially the carbon.
which is the metalloid causing fluidity, was driven from it; hence, when the pigiron was melted, it assumed the form of grain.
Mr. Samuel Baldwin Rogers introduced the present system of iron bottoms to furnaces, which obviated the deteriorating influence of the silicon due to the sandy bed of the Cort furnace, and eventually did away with the finery process.
The chamber the pig-metal is charged with consists of iron plates forming the bottom and sides, which are lined with refractory slags rich in oxides of iron.
In changing the heat, slags and scales from the hammers and rollers are thrown on the hearth or bottom, and on this the charge of pig-metal, consisting of 510 pounds to 540 pounds. Fuel is then thrown into the grate, and in about twenty-five or forty minutes this carburet of iron becomes liquid, and assumes the form of a molten plate of iron some one and a half to two inches thick Being heavier than the slags, the latter pass through it, and rise to the top. In passing the oxygen contained in the silicates combines with the carbon of the iron, and decarbonizes it; but unless the iron is agitated it will not become malleable.
Hence the puddler, with a bar called the
rabble, agitates the metal, and brings in contact the oxygen of the silicate with the carbon and other impurities of the iron.
As the carbon is leaving the metal, its atoms expand and become of less specific gravity, and it throws off carbonic oxide gas, the blue flame of which is plainly seen by any one who watches the process.
The puddler, at this stage, must be incessant in his operation, for the transformation scene is coming, and the crude iron is becoming malleable.
The boiling of the mass is kept up by the fresh energy of the puddler until, as the carbon diminishes, the atoms of the iron begin to knit or agglutinate together in a soft spongy consistency, the
cinder taking the place of the once molten iron.
The iron is now as sensitive to oxygen as a tropical plant would be if placed in a temperature at zero, and as the human lungs would be if inhaling pure oxygen: it lives, as it were, too fast It is at this point that smoke-preventers are puzzled; but a deoxidizing flame is kept on the iron while it is being kneaded and divided into balls, preparatory to being brought out of the furnace; and, when done, the lump is taken to the hammer and beaten into the required shape for rolling it into the puddled bar of commerce.
This operation is called
shingling.
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Plan of puddling-furnace. |
