Journal: Transactions of the American Foundrymen's Society V 70 P 612-621, 1962 (10 p)
Author: Dahlmann, A and Loehberg, K
Reactions between materials in close contact with metals
and alloys occur easier when the latter are in the liquid.
rather than in the crystalline slate. The possibilities for
such reactions to take place are many, e.g., reactions between
metal on the one hand and ceramics, molding
materials or the atmosphere on the other hand.
This paper deals with the reactions between liquid
metals and oxygen. Investigations of reactions between
liquid nonferrous metals and atmospheric oxygen, have
alreadv been carried out on frequent occasions. Reactions
between oxygen and metals, such as lead and zinc, have
been studied with respect to the products formed and
also the times taken for these reactions. It has been found
that the latter are functions of the temperature and the
composition of the allow and when plotted give either a
linear or a parabolic graph.
In contrast, reactions between liquid cast iron and
oxygen of the air. have hardly been investigated. This may
have stemmed from the belief that the slags encountered
in castings were, in many cases, products of the reaction
between melt and ceramic materials (in the widest sense).
In the course of this investigation it was found that
the observations published in the literature agreed with
the authors' findings. These confirm that the slags appearing
in spongy areas of castings arc developed bv the interaction
of liquid iron and the air: this occurring in the
ladle, in Ihe pouring stream or even in the mold.
This preliminary contribution to the clarification of
the problem of the kinetics of slag formation confirms
the fact, known from the literature, that such reactions
depend on the composition of the cast iron and especially
on the silicon, managanese and sulfur contents. The
author shows thai a close relationship exists between the composition of a cast iron, the temperature at which the
oxide films are formed and the composition of the slags
and their properties. In melts of cast iron that are rich
in sulfur a sulfide slag is the first to develop, followed by
a silicate slag. The temperature interval between the beginning
of oxide film formation and the complete covering
of the bath surface with slag is considerably smaller for
melts low in manganese than for melts high in manganese.
The possible cause of this may be a difference in wettability
of metal and slag respectively.
Summarizing, it is concluded that the formation of
spongy areas in an iron casting is determined by the
silicon, managanese and sulfur contents of the cast iron,
by the pouting temperature and by the time during which
the molten metal is exposed to the air.
$15.00 for members
$10.00 for corporate members
$30.00 for nonmembers
1695 North Penny Lane
Schaumburg, IL 60173
Tel: 800.537.4237, 847.824.0181