樹枝状偏析をもつ 3Cr-0.8C 鋼の再結晶と焼入組織

概要

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An ingot of 3%Cr-0.8%C steel having dendritic segregation was made by uniaxial freezing method. Specimens were cut from the ingot parallel to the freezing direction. They were heated at 1100 or 1200℃ for 30 min and hot-rolled to 10, 25 or 40% reduction and directry quenched, or 40% reduction and held for 10s after hot rolling and then quenched. The rolling direction was parallel to the freezing direction. After rolling and quenching, specimens were annealed at 1200℃ for 24 or 48h. The effect of rolling and annealing on homogenization of dendritic segregation was examined. The microstructure were observed at vertical section of the freezing direction. The results obtained are as follows ; (1) Dynamic and static recrystallization or grain growth were observed associated with hot rolling. These phenomena occured almost independent of the microsegragation in the specimen. (2) Martensitic quenched structure also formed independent of the microsegregation. Especially, lenticular martensite plates were extended to a large plate as if there is no influence of the concentration fluctuation. (3) Since the recrystallization associated with hot rolling refined the austenite grain size, some kinds of improvement of mechanical properties of the steel would be expected. The recrystallization, however, seemed to be not so effective to homogenization of segregation and it is less effective than the long time annealing at high temperature.
1979-08-01