Frostburg mining journal. [volume] (Frostburg, Md.) 1871-1913, 1891-10-03

Stocl has beeu dphHrd a. any kit!d %
iron which when heated to r1.llpss AMI
sal,,,ipnIy plunged into cold water he
comes hard; and every kind of naiea-
!,le or flexible iron that can be hardened
bv that process ia steel. But this d fl
milton, says An Occasional ContttbH5ur"
in the Iiechanicai News, is not Il .'Iica
Die to the steel of mild quality now
made for many mechanical uses. One
of the requisites for this mild steel is that
it will not harden after being heated to
a cherry red and plunged into water. To
include all the kinds of steel now use! in
agricultural and mechanical the better
definition of steel will be Il maileabl iron
combined with percentage OF carbon.
Chemically considered. steel occupies
half way position between wrought and
cast iron, wrought iron being simply iron
almost entirely free from carbon, while
steel that is to be tempered contains l to
II per cent of carbon.
The reason why this very slight change
in the chemical construction should pro-
duce such wonderful results in the prop
critics of iron and steel is as yet an un-
solved mystery. We know that a bar of
iron converted into steel becomes more
granular or open. and while it loses to
some extent its toughness. it gains, in
closeness of fiber
Blister steel is made by heating bars of
iron packed in charcoal in a furnace for
a period of from six to 10 days. When
the metal is withdrawn the bars are
found to be of crystalline texture, and
have a blistered surface-hence the name.
Cast steel was formerly made of blister
steel broken into fragments, melted in
crucibles, and cast into ingots but the
modern practice is to charge the c1uci-
bles with pieces of good Swedish or
American bar iron, adding charcoal and
black oxide of manganese. The heat of
the furnace soon seals the lid of the cru
cible, and the melting iron absorbs car
bon from the fumes of the charcoal, thus
shortening the tedious process of making
"blister" bar. The cast steel is rolled or
hammered from the ingot to any desired
bar, sheet, or plate.
The chief characteristic of steel con-
sists in its capability of being hardened
db'i ttlltl "IlGll tA I)OStNl 10 ut'dJ
it takes on in succession the following
colors:
1. A faint yellow, which indicates
proper temper for lancets or small cut
ters that require the finest edge, with but
little strength of metal.
?. A pale yellow, which indicates the
temper for razors and surgical instru-
mentS.
3. Full yellow for pen knives, etc. with
increased toughness.
4. Brown, with purple spots-that be-
ing for axes and carpenters TOOLS
;. Bright blue, for swords and watch
springs.
g. Full blue, for fine saws, daggers,
etc.
T. Dark blue. for large saws or instru-
ments that may be sharpened with file.
The above colors are based on steel
suitable for the requirements A piece
of steel suitable for razor. lancets, etc.
would not take the color indicated for
large saws, as that quality of steel is but
,ltle above the "blister" quality. The
finer steel is, the less heat it will temper
at. requiring a lower temper of color
Hecently there have been some valuable
discoveries in tempering, welding and
restoring Steel both from burnt or low
grade.