The Fairfield herald. [volume] (Winnsboro, S.C.) 1849-1876, 1867-11-13
Am|y Paper Devoted Science, inquiry, Industry Literature
c., WEDNESDAY, MORNING, NOVEMBER 1}, 1867.
Case Hardening Wrought aul Cast Iron

Uase- Hardening Wrought aul CAST Iron
The property of hardening Is not
possessed by pure mallcablc iron; but
We have now to explain a rapid and
partial process OF concentration, by
which wrought iron IS first converted
extcriorly into steel, and is subsc-
, qucntly hardened 20 that particular
depth, leaving tho central parts in
their original condition of soft, fibrous
iron. The process js called case hard
oatng, and is of great Importance in
mechanical arts. The principal! agents
ussd for case hardening arc animal
matters, as tho hocfs, horns, bones
and skins of animals These are char
red and coarscly compounded some
persons mix little common salt with
some of tho above. Che works should
be surrounded on all sides with Law
or from half an inch to an inch
thick.
The methods pursued by different
individuals do not greatly differ. For
example, the gunsmit' inserts the iron
work of the gun-lock i'll shcct-iron
case in the midst Of the bone dust,
1oftcn not bnmcd), the lid Of the box
is tied on with iron wire, and the Joint
lutcd with clay. It's then heated to
II redness as quickly as possible, and
retained at that heat from half an
hour to an hour, and t;c contents arc
then quickly immersedi in cold water.
The objects sought arc a stecly extc-
rior, with clean surface, covered
surface, covered with the mott,cd tints
apparently caused by The oxidation
from the partial admission Of air.
Some mallcablc iron cuttings arc
case hardened to admit of better
polish. This is usually done with
burnt bone dust, and 1t dull rcd
heat: they remain in the fire about
tw" or three hours and should be i'm
mcrscd in oil, as it docs not render
them quite SO brittle as when plunged
in water. 1t must le remembered
they arc sometimes changed through
out their substance into an inferior
kind of steel, bya process" that should
in such cases be called .cementation
and not case har}cning,. !. consequently
they will not endure whence.
The mcchanican and engineer use
horns, hoofs, bone dusts and leather,
ID ALLOW the period toEsXtcud from
two to eight hours, more generally four
to five. Sometimes, for its greater
penetration, the process is repeated
second time with new carbonaceors ma.
tcralS. Some open tho box and I'M.
merse the work in water direct from the
furnace; others with view TO preserve
better surface, allow the box to cool
without being opened, and harden The
pieces with an open fire as subsequent
operation. The carbon once added, the
work may be anncalcd and hardened
much the same as ordinary steel
When the case hardening is required
to terminate at any particular part, as n
shoulder, the object is left with n band
or projection, the work is allowed to
coil without being immersed in water
the band is turned of. and the work
when hardened in the open fire, is only
effected SO far as the original ccmrntcd
surface remains. This method was N.
troduccd by Mr. Roberts, who considers
the success Of tho case hardening pro-
cess to depend on the gentle application
of the heat; and that by rropcrimanagc.
mcnt, not to over heat the work, it may
be made to pcntrate three eights Of an
inch IN four or five hours.