1. Steel is a compound of iron and carbon; and, as there are several
methods by which the combination is produced, there are likewise
several kinds of steel. The best steel is said to be made of Swedish
or Russian bar-iron.
2. The most common method of forming steel is by the process of
_cementation_. The operation is performed in a conical furnace, in
which are two large cases or troughs, made of fire-brick, or good fire
stone; and beneath these is a long grate. On the bottom of the cases
is placed a layer of charcoal dust, and over this a layer of bar-iron.
Alternate strata of these materials are continued to a considerable
height, ten or twelve tons of iron being put in at once.
3. The whole is covered with clay or sand, to exclude the air, and
flues are carried through the pile from the furnace below, so as to
heat the contents equally and completely. The fire is kindled in the
grate, and continued for eight or ten days, during which time, the
troughs, with their contents, are kept red hot. The progress of the
cementation is discovered by drawing a _test_ bar from an aperture in
the side.
4. When the conversion of the iron into steel appears to be complete,
the fire is extinguished; and, after having been suffered to cool for
six or eight days, it is removed. Iron combined with charcoal in this
manner, is denominated _blistered steel_, from the blisters which
appear on its surface, and in this state, it is much used for common
purposes.
5. To render this kind of steel more perfect, the bars are heated to
redness, and then drawn out into bars of much smaller dimensions, by
means of a hammer moved by water or steam power. This instrument is
called a tilting hammer, and the bars formed by it, are called _tilted
steel_. When the bars have been exposed to heat, and afterwards
doubled, drawn out, and welded, the product is called _shear steel_.
6. But steel of cementation, however carefully made, is never quite
equable in its texture. Steel possessing this latter quality is made,
by fusing bars of blistered steel, in a crucible placed in a wind
furnace. When the fusion has been completed, the liquid metal is cast
into small bars or ingots, which are known in commerce by the name of
_cast steel_. Cast steel is harder, more elastic, closer in texture,
and capable of receiving a higher polish than common steel.
7. Steel is also made directly from cast iron, or at once from the
ore. This kind is called _natural_ or _German_ steel, and is much
inferior to that obtained by cementation. The best steel, produced
directly from the ore, comes from Germany, and is made in Stiria. It
is usually imported in barrels, or in chests about three feet long.
8. Steel is sometimes alloyed with other metals. A celebrated Indian
steel, called _wootz_, is supposed to be carbonated iron, combined
with small quantities of silicium and aluminum. Steel alloyed with a
very small proportion of silver, is superior to wootz, or to the best
cast steel. Some other metals are also used with advantage in the same
application.
9. Steel was discovered at a very early period of the world, for aught
we know, long before the flood. Pliny informs us, that, in his time,
the best steel came from China, and that the next best came from
Parthia. A manufactory of steel existed in Sweden as early as 1340 of
the Christian era: but it is generally thought, that the process of
converting iron into steel by cementation originated in England, at a
later period. The method of making cast steel was invented at
Sheffield, in the latter country, in 1750, and, for a long time, it
was kept secret.
10. It has been but a few years, since this manufacture was commenced
in the United Sates. In 1836, we had fourteen steel furnaces, viz.; at
Boston, one; New-York, three; Troy, one; New-Jersey, two;
Philadelphia, three; York Co., Pa., one; Baltimore, one; and
Pittsburg, two. These furnaces together are said to be capable of
yielding more than 1600 tons of steel in a year. The American steel is
employed in the fabrication of agricultural utensils, and it has
entirely excluded the common English blistered steel.
[Illustration: BLACKSMITH.]