Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1891-11-11
OUR MAIL POUCH.
The Processes of TouEhening Steel.


To the Editor ofThe Dispatch:
Ever since the first test made some months
ago with the 3-inch ntckel-steel plates with
hardened surfaces, vast amount OF inter-
est has beeA awakened on the process of
surface carbonization, or, as some Eastern
papers are pleased to term it, "Harvey1z-
ing" But now a keener interest Is taken IN
the subject since the more Important tests
OF the thicker and heavier plates lulmeh-
sions, l01< inches thick, feet high, and feet
wide), took place at Indian Head. on the Po-
tomac river, near Washington, D. T., Satur-
day, October 81
1t is not my intention to criticise the Har-
vey process nor to dispute their claim to
discovery for which they have been recent
ly granted patents, but will say, and that
most emphatically, that iron and steel
workers-now that they have been let into
the secret-fail to see anything that is new
in 1t. The principle-and I ought to say the
practice-was discovered so long ago that
the name Of the discoverer has been forgot
ten. 1t has been known more than 2oO years
that when wrought iron is enveloped In
powdered charcoal and heated to reoness
for long time it gradually becomes carbon
lied and converted into steel, the deposi-
ton OF carbon commencing at the OUTSIDE
and gradually penetrating inward In pre-
cisely the same way as that in which the de-
"
facture of malleable cast iron, . longer time
being consequently requisite for carDonlza-
tion of thicker than of thinner bars; the
name OF the inventor of this process, now
ever, has been forgotten.
PractIced in the Sixteenth Century.
In the middle of the sixteenth century it
was known that when bar OF wrought iron
was kept immersed long time in molten
cast iron it gradually became acierated by
taking up carbon from the cast iron; this
process is closely allied to cementation in
solid carbon, and was probably the forerun-
ner thereof. We may presume that In the
first place it was the result Of accidental OBJ
servation. 1t was described as being in ac-
tual use about that period by various
writers, notably Biringuecio In l5aO ana AS-
ricOla in 1861.
Early in tho eighteenth century Reaumur
investigated the character Of the process,
bar of iron of 0.2 inch in thickness was car
bonized in six hours to the same extent as
another bar of the same metal of 0.45 inch In
thickness in about 36 hours.
Let us see now what relation the Harvey
process bears to case hardening, which, OF
course, means, too. surface carbonization.
This operation is essentially the reverse
of that by which cast iron is converted into
malleable iron. In the latter the carbon is
gradually removed, the outer portion being
first affected; in the former carbon is added
to the exterior layer of a malleable iron ar
and power of resisting wear and tear by
superficial conversion into steel.
The Operation Practically Cementation.
As applied to larger articles in which the
steely coating is required to be of more than
just perceptible thickness, the operation
is essentially that of cementation, the iron
articles being packed in an iron chest or
box in charcoal reduced to very coarse
powder tburnt or charred leather, hoofs,
heated to a red heat for sufficient length
OF time, when the chest is Withdrawn from
the furnace and the articles chilled by
quenching in water or oil so as to harden
1t was the practice before the advent of
steel to carbonize the surface of the iron
rail, which was effected by the following
method: Charcoal, soda ash, and limestone
crushed small were mixed together in the
proportion of l cwt. Of the first to one
stone of each of the others. and charged into
the case-hardening furnace between success
sfve tiers of rails. The rails remained in the
furnace 60 hours; when taken out they were
covered with sand till cold. In some Of the
rails treated by this process invented by
Dodd, it was found that carbonfzation ex-
tended inward for nearly a quarter of an
inch.
Similar to the Case-Hardening Process.
Now were to describe the so-caIled Har-
vey process it would be-aside from few
unimportant details-but repetition of the
description given of the case-hardening
process. In the specifications sent to the
Patent Office, we find that great stress is laid
on the manner of charging the plate in the
furnace in Embedding it in finely powdered
clay so that its upper extreme sur
face only will be exposed. We also find
in case hardening, when only portion of an
iron object is required to be case hardened,
a coating of clay is applied to that part of
the material not required to be hardened
This prevents the ready access of carbon
and carbon oxide to the covered up part
and entirely prevents alteration thereat
Knowing all this, and being fully convinced
that the Harvey, process is but a modifica-
tion of case hardening or cementation, the
question naturally will arise why were they
granted patent for u process that belongs
to every man?
But after all their case has a precedent.
The conversion of cast iron into malleable
iron and steel by Decentralization was
described by Reaumur in 1722. and we find
that in 1S04 a patent for this process was
granted one Lucas, and Brown and Lennox
some so years later. DI OXIDE.
PITTsBURG, November 9.