The Iola register. [volume] (Iola, Allen County, Kansas) 1875-1902, 1884-09-26
Smelling and Casting OF Iron.

The mettalurgical processes en-
ployed in the extraction or iron pro-
duce metal which contains carbon,
silicon. manganese, and other sub
stances. Pure iron, having a very high
fusing point, is not well applicable to
foundry purposes; the material we
have to examine is iron combined with
carbon. The presence of carbon. it be-
ing combined and disseminated as
graphite through the iron. causes q
lowering of the fusing point. When
pig iron is molten in cupola furnace,
the air comes in contact with particles
of the liquid metal and the carbon
thereof; the metal is partly decarbon-
lied. The impurities, silicon, man
ganese. and small quantity of iron are
converted into oxides, producing the
Stag.
Other products of oxidation, carbonic
oxide and iron oxide. are dissolved in
the molten iron. The air blown into
the furnace generally contains aqueous
vapor. and by its action upon burning
coke hydrogen is generated. Molten
iron, possessing the property of dissolv-
ing three times its volume of hydrogen,
as has been shown by the latest inves-
legations, is thus charged with carbonic
oxide, hydrogen and iron oxide. On
cooling of the metal the gases are
emitted; they are the cause of the
spongy, pumIce stone-like surfaces
structure observed ON solidified metal
lie masses.
Iron being molten at low tempera-
ture, and then tapped off and poured
into moulds, liDerates the dissolved
gases within the mould. The structure
of such casting exhibits the presencs
OF cavities and high degree of pOros-
ity. Such cavities have pease-like shape
near the surface, and assume that of q
sphere toward the center of the metal;
they are sometimes connected with each
other by small channels. When heated
more rapidly and far above its fusing
point. iron becomes more applicable to
foundry purposes. The molten metal
remaining for some time in the ladle
and being agitated by the aid of bar
before it is poured into the moulds,
permits free CELEBRATION of dissolved
gases.
The property of iron of absorbing
gases and iron oxide is increased by re-
melting of iron; for homogeneous cast
ings iron must be used which has not
previously served the same purpose.
The spongy structure of a casting Is al
so caused by the moulding material.
When the Orifices of a mould become
gradually filled with molten metal. the
escape OF gases depends on the phy sical
nature of the moulding material. The
latter containing moisture and organic
substances generates aqueous vapor
and other gases, which cause the forma-
ton of surface cavities. These cavities
are covered with film of OK died
metal, while those produced by dis
solved gases have bright metallic sur.
face.
The difficulties involved in the cast
ing Of homogeneous articles are partly
overcome by the use Of a suitable por-
Gus sand. Another class of cavities Is
that called druse. The cavities of n
druse are studded with iron crystals Of
a dendritic form. The formation Of
these cavities is caused by abnor-
NAL shrinkage during solidffi-
cation. Another phenomenon gener-
ally called sucking must be assigned to
the same cause; it is generally observed
on parts of castings where large
quantity of metal has been collected.
1t is therefore advisable in the manu-
facture of castings to give them an IuaI
wall thickness, which has the advau-
tage that the tension is most equally
distributed throughout the mass. On
cooling of the liquid metal within the
mold, the particles which are in con-
ia with the mold are sooner solidified
than those more distant, and promote
q motion Of the liquid material from
places of greatest to such of less accu-
mutation, thus forming druses.-Metat-
idr6eiter.