An Improvement in the Manufacture of Cast Iron.
Year: 1890

page_text: Date of Application, 21st Oct., 1890-Accepted, 17th Jan., 1891
COMPLETE SPECIFICATION.
An Improvement in the Manufacture of Cast Iron.
I, JOSEPH B. RENSHAW, of 80 State Street, Hartford, Connecticut, one of the
United States of America, Ironmaster, do hereby declare the nature of this invention,
and in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
This invention is applicable to the treatment of gray iron as used in foundries; and
it consists in a process of eliminating, from melted iron, surplus graphitic carbon, and
also a substance resembling carbon, which is called "kish," and is also produced in
blast furnaces, and which, when in excess, causes kishy unsound surfaces on castings.
The process involved in this invention is as follows. Iron oxide is prepared or
procured in pulverized form, in any convenient manner; and sawdust, shavings, straw,
or other vegetable fibre, of which the wood material used by upholsterers and called
"excelsior" is a good variety, or any substance which, when wet, will absorb and hold
a due proportion of iron oxide, and prevent it from cinderating when in contact with
melted iron, is procured or prepared and saturated with water to a suitable degree,
of which three pounds of water to a pound of fibre or other substance is a proper
example. The iron oxide is then thoroughly mixed with the saturated fibre, and this
mixture results in the absorption of the iron oxide by the fibre; and in a consequent
product resembling such fibre, except in being much heavier in weight and darker in
colour. That product, when sufficiently dried, is preferably divided into definite
portions of equal or unequal quantities, and placed and kept in paper bags or other
packages for ultimate use.
When it is desired to eliminate graphitic carbon from molten iron, a suitable amount
of the described product is placed upon the iron before it is melted, or in the iron
when it is being melted, or in a ladle into which melted iron is to be poured, as the
case may be.
From one to three pounds of the dried compound of vegetable fibre and pulverized
iron oxide, is enough for one hundred pounds of iron; and the amount of the
compound may be varied, within these limits, according to the amount of graphitic
carbon which is to be eliminated from that iron.
The enclosing package is duly consumed, and the contents thereof discharged upon
or into the molten mass; and as the fibre burns, the iron oxide is released in separate
particles to the action of the heat, and to the chemical actions consequent upon its
contact with the melted iron. Those chemical actions consist in the union of the
oxygen in the iron oxide with a corresponding quantity of the graphitic carbon in the
melted iron, thus forming carbonic oxide gas, which passes out of the molten mass into
the air; and also consist in another quantity of the graphitic carbon in the melted
iron uniting with the iron of the iron oxide, which latter is thus incorporated with the
molten mass. Thus the proportion of graphitic carbon in the molten iron is reduced,
and that reduction may be made more or less extensive according to the purpose for
which the iron is ultimately to be used. For example, the proportion of graphitic
carbon in the molten iron, may be reduced by this process, from three and one-half
per cent., which is a suitable proportion for one kind of castings, to one per cent.,
which is a suitable proportion for another kind of castings.
It is not new to treat molten iron by means of introducing oxide of iron into the
molten mass; but I believe it is original with me to introduce iron oxide into molten
iron by first mixing pulverized iron oxide with vegetable fibre, and then casting the
combined product into contact with the iron from which the graphitic carbon is to be
eliminated.
The particular utility of my invention resides in the fact that it is superior to casting
pulverized iron oxide upon or into melting or melted iron, because such pulverized

page_text: iron oxide when thus cast, is blown away by the blast, which supports the combustion
of the fuel and maintains the fluidity of the iron, before it can form the chemical
unions above indicated; and also resides in the fact that it is superior to casting a
compact mass of iron oxide upon or into melting or melted iron, because it secures a
more even distribution of the iron oxide, and because such mass, when thus cast,
undergoes immediate melting of its exterior particles and the consequent-conversion of
those particles into a metallic iron shell, which thereafter encloses the interior particles
of the mass, and prevents those portions from operating as above set forth on thej
graphitic carbon in the melted iron.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim 'is:
J
The process of eliminating graphitic carbon or kish from melted iron, by means of
iron oxide; which consists in first mixing vegetable fibre or its equivalent, with
pulverized iron oxide, and then adding the compound to the iron to be melted or being.
melted or previously melted; all substantially as described.
Dated this Ninth day of October 1890.
JOSEPH B. RENSHAW.