The Roanoke times. [volume] (Roanoke, Va.) 1890-1895, 1891-09-05
TEMPERiNo STEEL
Pafc Yellow for Razors and Darix Bfuo
for Saws tho I'gopcr Coiors-

Tor SAWS tho l'gopcr Colors-
Steel has hccn defined as any kind Of
iron which when heated to redness and
suddenly plunged into cold winter be-
comes hard; and every kind of mallea-
bic or flexible iron that can be hardened
by that process is steel But this def
milton is not applicable to the steel of
mild quality now made for many me-
chanical uses, says the Mechanical
News Ono of the requisites for this
mild steel Is TINT IL will not harden after
being heated to a cherry red and
plunged into water. TO include all the
kinds of steel now used in the asrri-
cultural and mechanical industries, the
better definition of steel will be, II NAL
leaole iron combined with percentage
of carbon Chemically considered, steel
occupies halfway position between
wrought and cast iron, wrought iron
being simply iron almost entirely free
from carbon, while steel that Is to
DC tempered contains one TO one and
onc-half per cent of carbon
Tho reason why this very slight
change in the chemical construction
should produce such wonderful results
in the properties of iron and steel is as
yet an unsolved mystery. We know
that bar of iron converted into steel
becomes moro granular or open, and
while it loses to some extent its tough
ness, it gains, instead elasticity, great
or strength and closeness of fiber.
Blister steel is made by heating bars
of iron packed in charcoal in o furnace
for a period of from six TO ten days.
When the metal Is withdrawn the bars
are found to be of crystalline texture.
and have blistered surface-hcnce the
name Cast steel was formerly made of
blister steel broken into fragments,
melted In crucibles and cast into in1ots;
but the modern practice is TO charge
the crucibles with pieces of good Swed-
1sh or American bar iron, adding char
coal and black oxide Of manganese.
The heat of the furnace soon seals the
lid OF the cruciblc, and the melting iron
absorbs carbon 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 bur, sheet or
plate
The chief characteristic of steel con-
sists in its capability Of being hardened
and tempered, and when exposed to
heat it takes on In succession the fol-
lowing colors:
L faint yellow. which indicates q
proper temper for lancets or small cut
ters that require the finest edge, with
but little strength of metal
9. pale yellow. which indicates the
temper for rasors md surgical instru-
mentS
B. Full yellow. for penknivcs, etc,
with increased toughncss.
d Brown. with purple spots-that be-
Ing for axes and carpenters tools.
5. Bright blue, for swords and witch
springs.
G. Full blue, for fine saws, daggers,
etc.
{. Dark blue, for large saws or In.
struments that may be sharpencd with
q file
The above colors are based on steel
suitable for the requirements A pieco
OF steel suitable for rnzors, lnncets
etc, would not tnllc the color indicated
for large saws, rs that quality of steel
Is but little above the blister" quality
The finer steel IS the less heat it will
temper at, requiring n lower color CT
temper. Recently there have been some
valuable discoveries in tempcring, weltl-
ing and restoring steel, both from burnt
or low grade.