Iron and Aluminum. [Volume: 8, Issue: 2, 1888, pp. 116-122]

No. 2,]

CHARCOAL IRON WORKERS.

117

mechanically mixed with the iron in the form of graphitic carbon,
when it becomes visible. Other elements commonly found in cast
iron are phosphorus, sulphur, manganese and silicon. The natural
condition of carbon in iron is the combined state. The presence of
silicon drives a portion of the carbon into the graphitic state. Sulphur, manganese and phosphorus do not cause the carbon to leave
its natural combined state, and if silicon be present these elements
either drive it out or overpower it. Carbon is, therefore, a passive
element, and is made to change its form by the presence of other
elements. It is this change of carbon which indicates, to the eye,
the influence of any element upon the cast iron. Iron and combined carbon, or carburetted iron, is called "white iron," the grain
is generally very fine, and often even, and the metal is very hard.
Graphite darkens the fracture until it becomes a very dark gray,
and the grain is coarse and irregular. With increase of graphite
the metal becomes soft. * * * * *
Fused wrought iron, or a mixture of cast iron and steel or steel
alone, either of which would make castings full of blow-holes, will
make solid and homogeneous castings if as small a quantity of
aluminium as one-tenth of 1 per cent is added just before pouring.
Also that sudh addition causes the iron to remain fluid long enough
to allow its being cast into molds. * * * *
Regarding the physical tests, we should state that we use two
bases —one a white iron, with composition, Si. 0.186, P. 0.263,
S. 0.0307, Mn. 0.092; the other a gray Swedish iron marked
"FLM." with composition, Si 1.249, P. 0.084, S. 0.04, Mn. 0.187.
The ferro-aluminium contained Si. 3.86 and Al. 11.42 per cent.
* * * - * * *
These sound castings of the white base alone resisted a weight
of 379 pounds. With one-tenth of 1 per cent. of aluminium added,
it resisted 545 pounds, a gain of 166 pounds, or about 44 per cent,
from this small addition. Measuring the resistance to impact the
white alone was 239 pounds; with aluminium, 254 pounds, or
about 6 per cent. gain. The castings appear of slightly finer grain,
and the character of the crystallization is somewhat different, but
the secret of the strength lies in the closing of the spaces between
the grains-or, in other words, in the increased solidity of the casting. No other change is noticeable in the metal. * * *
But the results of the tests show conclusively that the aluminium