The diamond drill. (Crystal Falls, Iron County, Mich.) 1887-1996, 1891-07-11
rEMPERiNo STEEL.


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saws the Proper coIors-
Steel has been defined ms any kind
OF iron which when heated ~ redness
and suddenly plunged into cold water
becomes hard: aud every kind OF NAL
leablc or flexible iron that can be
hardened by that process Is steel. But
this definition In not applicable To tha
steel OF mild quality now made fo'
many mechanical usos. says the Me-
chanical News. One OF the REQUISITES
for this mild steel is that IL will not
harden after being heated 10 IA cherry
red and plunged into water. To In
clnde all the kinds OF steel now used
In tho agricultural and mechanical In
dustries. the better definition OF steel
will be. "a malleable iron combined
with "a percentage OF carbon. Chemi-
cally considered. steel occupies a half
way position between wrought andcass
iron, wrought iron being simply iron
almost entirely free from carbon.
while steel hat is To be tempered con-
tains l 10 IL per cent OF carbon.
The reason why this very slight
change in the chemical construc.ion
should produce such wonderful results
In the properties Of iron and steel il
as yet IN unsolved mystery. We know
that a bar OF iron converted into steel
becomes more granular or open. and
while il loses to some extent its tough
ness. it gains. instead. elasticity.
greater strength and closenoss OF fibre.
Blister steel Is made by heating bars
OF iron packed In charcoal in "A furnace
for a period of from six 20 ten days.
When the metal IL withdrawn the bars
are. found To be OF crystalline texture.
aud have a blistered surface-hence
the name. Cast steel was formerly
made OF blister steel broken into frag-
ments. melted into crucibles and cast
into ignots; but the modern practice is
to charge tho crucibles 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 crucible. and
the melting iron absorbs carbon from
the fumes of the charcoal. thus short
ening the tedious process OF making
.'blister" bar. The n steel Is rolled
or hammered from the ignot TO any
desired bar. sheet. or plate.
The chief characteristic OF steel con-
sists in its capability OF being hard
encd and tempered, and when exposed
to heat IL takes on in succession the
following colors:
/. A faint yellow. which indicates "a
proper temper for lancets or small cut
ters that require the finest edge. with
but little strength of metal.
2. A pale yellow. which indicates
the temper for razors and surgical i'm
struments.
3. Full yellow, for pen-knivcs, ETC..
with increased toughness.
4. Brown. with purple spots-that
being for axes and carpenters tools.
5. Bright blue. forswords and watch
springs.
6. Full blue, for fine saws, daggcrs.
etc.
Z. Dark blue. for large saws or in
struments that may be sharpened with
a file.
The above colors are based on steel
suitable for the requirements. A piece
OF steel suitable for razors, lancets.
etc. would not take the color indicated
for large saws. rs that quality of steel
is but little above .'blister" quality.
The finer steel Is the less heat IL will
temper al, requiring n lower color OF
temper. Recently there have c
valuable discoveries In tempering,
welding, and restoring steel, both
from burnt or a low grade.