Abstract
Solidification behavior of high-nickel grain roll materials has been studied experimentally with a unidirectional solidification method. Two specimens were employed; A had the standard chemical composition, and B had the composition which promoted white iron solidification. Solidification structures were observed, and the amount of graphite was measured. The temperature difference between ledeburite (γ+Fe3C) and austenite-graphite (γ+G) eutectic fronts was measured, and there appeared to be a good correlation between this value and the amount of graphite. Then the positions of the two eutectic fronts and the temperature difference were discussed with regard to solidification parameters.
The results obtained were as follows:
(1) The critical cooling rate of transition from white to mottled iron in A is 0.12-0.15 K s–1, and for B, it is 0.050-0.067 K s–1.
(2) The austenite-graphite eutectic front precedes the ledeburite eutectic front at a smaller growth rate, while the latter forms first at a larger growth rate in A. Ledeburite always forms first in B.
(3) The sequences and temperature difference of both eutectic fronts agree with the results calculated using the Fe-C binary eutectic solidification model.
