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Eisengusswerkstoffe
Dokumenten-Nummer: 57879
Tagungsbeitrag
Nakae, Hideo; Fujimoto, Kyohei
Publikationssprache: Englisch
Influence of Ti on Graphite Morphological Transition in Flake Graphite Cast Iron
Einfluss von Titan auf den Graphitmorphologieübergang bei Gusseisen mit Lamellengraphit
The morphological transition from the A-type to D-type graphite (undercooled graphite) in cast iron has been studied
using Fe-3.5%C-2.0%Si-0/0.1%Ti samples. The samples were prepared using a high frequency induction furnace flowing
Ar atmosphere using 0.25% steel rods with or without Ti addition. The samples had Ti contents that ranged from 0 to
0.10% at 5 different levels by the addition of sponge titanium. The cooling curves of these melts were measured in a
shell mold with an inside diameter of 30 mm and 50 mm height and in four BN-coated steel cup molds with a volume of
30 ml each. The cooling curves were measured by CA thermocouples located at the center. The cooling curves were
differentiated to determine the transition points, namely the onset and end points of the eutectic solidification. Three
out of the four samples, solidifying in steel molds, were quenched during the eutectic solidification and their
macro-structures and micro-structures were observed for the determining the solidification mode. The volume fractions
of the D-type graphite area in the samples were measured using 30 microscope images of 50 x magnification, and their
eutectic temperature was also determined using their cooling curves. The volume fraction of the shell mold samples
increased with the Ti addition from 5% to 55%, and if the Ti content was greater than 0.05%, the acceleration occurred
with their maximum undercooling, Delta TMAX. The critical undercooling temperature, TA/D, and the critical
solidification rate, RA/D, of the A-type to D-type graphite transition were determined by comparing the volume fractions
to the solidification time. The Delta TMAX and TA/D values increased with the Ti addition. This is the main reason why
the Ti addition accelerates the D-type graphite increase.
Waseda University, Tokyo, JP
Erscheinungsjahr 2010
S. S.25-30
Seiten/Bilder/Tabellen/Quellen: 6S
Eisengusswerkstoffe
Dokumenten-Nummer: 57910
Tagungsbeitrag
Naydek, Vladimir L.; Gavrilyuk, Vladimir P.; Neizhko, Ivan G.
Publikationssprache: Englisch
On the theories of graphite formation in iron
Über die Theorien der Graphitbildung im Gusseisen
The paper reviews the theories of graphite formation in iron. The hypothesis of nodular graphite formation in pure
iron-carbon alloys is proposed and discussed. Most theories considered flake graphite as the initial form of graphite in
iron. Reseachers considered that spheroidising results in changing form of graphite in iron from the "natural flake one"
to nodular one. But our hypothesis considers that in pure iron-carbon alloy nodular graphite should be formed. That is
why it is necessary to study how surface active elements and impurities prevent formation of nodular graphite and
facilate formation of flake one. Many experiments were conducted from the beginning to study the mechanism of
nodular graphite formation. The potential of carbon as chemical element is almost unlimited. At present it is clear only
that graphite grows in case of low content of sulphur and oxygen (and some other elements) and preventing them to be
in the melt as surface active elements.
Physico-Technological Institute of Metals and Alloys, NASU, Kiev, UA
Erscheinungsjahr 2010
S. S.48-51 (4 Seiten, 5 Bilder, 7 Quellen)
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