Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1892-03-03
MILD STEEL FUSION.
A Phenomenon in the Melting C0ndi-
tions of This Metal.
THE INTERIOR MAY BE MOLTEN
While the Exterior Remains in Perfectly
Solid State.
A DISCOVERY OF GREAT IMPORTANCE

A UlSCUVEk1 UF UhGAI 1MIUhlANOG
The discrepancies in regard to the melt
ing points Of certain iron and aluminium
alloys. as stated by different observers-a
matter to which forcible reference was made
by Mr.. Hadfeld in his paper on aluminium
steel, which appeared in the second volume
of last years Transactions of the London
Iron and Steel Institute-has induced
E. J. r. Carulla to bring to notice
circumstance which, while he does
not profess to say it explains the varla-
tions referred to, may yet have some bear
ing upon them, and is otherwise OF
interest to iron and steel users and manu-
facturers
The phenomenon in question is the re-
markable one that the interior Of piece of
mild steel may be raised to the fusing point
while the outside remains in the solid state,
Just as if one were to try. to melt an iron
tube closed up at each end, and filled with
some metal Of lower melting point than
iron, in which case the heat would pene-
trate through the iron and liquify the in
terror long before the tube itself would be af-
fected, and if there should happen to be some
outlet or weak place in the tube it might be
left completely empty. Bessemer steel
makers, especially those who may have en-
ployed the system of upward casting, will
be reminded of the shells of ingots accident
ally obtained in the melting shop by an in
cautious act, produced, however, by diff
ferent process, viz: by the cooling OF the
outside while the interior of the ingot re-
mains in molten state.
Shells Obtained Many Years Ago.
Shells have also been obtained by alter
ing the nature of the exterior OF apiece OF
cast iron, so as to leave the interior more
fusible than the outside. Henry Horne, so
long ago as the year 1873, in his Essays
Concerning Iron and Steel" after describ-
ing Reaumur's method Of softening cast
iron by means OF mixture of calcined
bones and powdered charcoal, goes on to
say:
'I have myself tried the truth of the
hypothesis in a rough way, as far as neal
ing, or merely reducing, has any concern in
the matter, by great number of expert
ments, two only Of which judge necessary
to recite by way of specimen. had several
small ingots of cast-iron, about three
quarters of an inch thick; these put into
q crucible covered all round with the matter
above described, and in that situation COM
mitted them to the fire, where suffered
them to remain sufficient time, then took
them out and gave them strong heat, when
the exterior parts were become capable of
bearing even welding heat, while the in
terror suffered an easy dissolution, and ran
out into the fire. ran some other ingots
in the form of pistol barrels, which
having treated in the same manner,
the same consequence ensued; the exterior
cases, as before, remained firm and Stable,
while the interior dissolved and ran out,
and left cases in the entire form of pistol
barrels"
The instance, however, to which this
paper refers, is altogether different from
those just mentioned, and it will be perhaps
best to give an account as accurately as can
now be remembered of the circumstances
under which the observation was made
Some years ago the writer was engaged at
Sheffield in the operation of melting, in pots
or crucibles, steel intended for the manu-
facture of wire ropes, the material charged
being mainly Bessemer scrap of varying
carbon contents, which, however, by the
process became averaged, and the resulting
product attained uniformity that was
much appreciated for the purpose named.
What a Broken Crucible Disclosed.
1t happened on one occasion that cruci-
BILE gave way in the furnace Just as fusion
was nearly complete, the greater part of its
contents running out into the fire. The
melter happened at that moment to bring
the crucible out, and what he supposed to
be an empty pot was found to contain
number of shells, having the shape of the
pieces of steel originally charged, and show
ing that the interior of these had undergone
fusion while the outside envelope remained
soIid-a fact leading to the conclusion that
the melting point of the interior mass was
lower than that of the exterior coating
Two of the pieces found in that crucible
are now shown. The larger piece, about 81
inches by 15s inches square, must originally
have weighed about Al ounces. 1t is now q
shell of Az ounces. The smaller piece,
about inches by ~ inches, by "A inch,
will originally have weighed approximately
21L ounces; its she'll now only weighs 81
ounces From these figures it will be seen
that the larger piece lost by fusion of its
interior about 261@ ounces, or 64H per cent
of the whole; whilst the smaller piece lost
IN ounces, or 66H per cent of the whole in
the same manner-two results that agree in
a remarkable way. 1t would therefore
as if mild steel of the dimensions
given. having sectional area of
from 2 to 21z square inches, pos
sessed coating of skin of about one
third cf the whole mass with a higher
melting point than the remaining two-thirds
forming the interior.
How far such fact may have affected the
observations on the melting points OF steel
and aluminium alloysreferred to at the COM
mencement of this paper it is impossible to
say, but it will be perceived that if the same
occurred in their case as that
which has been described, discrepancies in
q number of observations are easy to ac-
count for. 1t is to be regretted that the
composition of the steel as it originally
went into the crucible is unknown.
Resistance to Fusion Easily Understood.
Scrap was being melted, much of which
would be from cut up rail-ends, but the square
piece looks like portion of billet which
might have been of milder steel. At any
rate, both shells now only contain mere
trace of carbon, the amount not reaching to
OIL per cent, so that their resistance to
fusion can be easily understood.
The phenomenon referred to is, however,
interesting in other ways besides in its re-
lating to the subject of melting
points. Some such result might, for in
stance, be expected from the facts COM
municated to this institute in 1881 by
Mr.. Stubs, and subsequently corroborated
by Mr.. Snelus, that carbon, sulphur, and
silicon become concentrated in those por-
tions of the ingot that remain fluid the