The Opelousas patriot. [volume] (Opelousas, Parish of St. Landry, La.) 1855-1863, 1856-05-24
Valuable Experiments with Cast Metals

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A finely executed and comprehensive work
has just been published by authority of thu
Secretary of war, containing reports Of officers
belonging to the United States Ordnance De.
partment, on the above named subject. The
years, and were made to test the strength ant
other properties Of metals employed in the
manufacture Of cannon. The work is a scien
tiic one of great value, especially the informa
ton it contains relating to the nature aud
treatment Of cast-iron, a material Of deep inter
est to so many millions Of people in our OWL
ard other countries.
Tie experiments were mostly conducted
under the charge Of Major w. Wade, who
details them in an exceedingly clear and inter
esting manner. One new fact developed by
them is, that iron fused a number of times M
to a certain point, is thereby greatly improved
in strength. In trials with some iron, it was
found that its transverse strength was nearly
doubled by being melted and cast four times
This is a discovery of great Importance to all
engineers and c~ast-iron founders. AT the
South Boston Foundry, experiments were made
to test the strength Of cast-iron, which had
been submitted to fashion during different
periods of time. Eleven thousand pounds {
iron were cast into four six FOUNDER guns ; one
after the metal had been under fusion or melted
half All hour; the second, under fusion an hour
and a half the third, under fusion three hours
and the fourth, under fusion three hours and
three quarters.
The gun first cast burst at the thirty-frst
fire, the second at the thirty-fourth the third
was fired thirty-eight times, and remained I'm.
broken. Thus the strength of the metal seemed
to increase in the ratio corresponding to The
period of fusion, or under which it was kept in
the highest molten state, and it might have
been inferred from this that the fourth gun
would have been the strongest of all. Instead
of this being so, however, it proved to be the
weakest, for it burst at the twenty-ffth dis
charge. In view Of these experiments, Major
Wade, in tits report, says :. these results ap-
pear to establish satisfactorially the fact, that
a prolonged exposure Of liquid iron to an
intense heat does augment its cohesive power,
and this power increases US the time of its
exposure up to some mot we'll ascertaiucd)
limit, beyond which the strength Of the iron is
diminished. This is q newly developed fact,
in relation to cast iron, subject to conclusions,
of deep import to all engineers. Experiments
were also made to test the transverse strength
of cast iron bars, two inches long, the metal of
which was kept under fusion during different
periods of time. These bars were set on SUP
ports twenty inches apart, and the breaking
force was applied at the middle. The results
obtained from four castings were in favor of
that which wa kept fused longcst-threa
hours. On this head the report says, " from
this it appears that the cohesive power of the
iron. so far as it can be shown by its capacity
to resist transverse strains, is increased 60 rer
cent. by its continued exposure in FUSION
This is also a fact of Importance to engineers
and architects, regarding girdcrs or beams,
subject to q crushing force.
In most of the books which treat Of the
strength of cast iron, the resistance which it
opposes to certain strains is given, but little
useful information can be obtained in them re-
garding the very great difference of strength in
different kinds Of cast iron. But as the density
between the lower and higher grades of this
metal differs as SO to IA difference of 81
pounds per cubic foot, and as the tcnacity of
the metal has a relationship to its density, it
was found by these experiments that cast iron,
having a density of 5000, had only IA tenacity
Of 5000, while that having a density of 7,4o6,
had a tenacity of 1870.
Castings Of the greatest weight, according to
their size, are by far the strongest, and weigh
ing them is a ready means Of Judging compar-
atively of their strength.
Some important facts were developed in re-
lation to the cooling of heavy castings. At
the Fort Pitt Iron Works, two eight-inch
guns were east. one of each in the common
way, solid, and one Of each with q core on
a tube of iron, through which water was made
to circulate after casting, to cool it from the