Graphite Re-precipitation in Calcium Graphite Steel

概要

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Metastable primary cementite precipitates preferentially from the γ solid solution of hypereutectoid Fe-C steels, without stable graphite precipitation, by the ordinary solidifying process. In the present experiment, it was found that graphite re-precipitation readily occurred from the γ solid solution of calcium-treated hypereutectoid cast steels during the air-cooling or the furnace-cooling after the heat-treatment in the y region from 1060℃ to 1210℃. In calcium-untreated cast steels, graphite precipitation was observable mainly along the grain boundaries of dendritic structures by the furnace-cooling from 1000℃ immediately after rapid cooling from the molten state to that temperature. If crystal imperfections such as voids are formed in the γ solid solution, the graphite precipitation would more readily occur in those sites, because the activation energy for graphite nucleation decreases due to decreasing interfacial energy and strain energy. On the basis of the experimental results hitherto obtained, the mechanism of graphite precipitation from the γ solid solution was considered.
東北大学の論文