Original paper(Vol.45 No.3 pp.316)

Relationship between microstructure and impact strength of ferritic ductile cast iron for cask use

Sunada Hisakichi; Fukaura Kenzo; Sato Takayuki

Abstract:Ferritic cast iron with spheroidal graphite for cask was in this study. The material was separated into five parts along the radius direction of the vessel, and the relation between microstructure and Charpy impact behavior was investigated. The results obtained are summarized as follows;
(1) The size of graphite and the distance between graphite nodules increased near the center in the section of the vessel, and the number of graphite nodules inversely decreased. (2) Fast Fourier Transforming treatment used to analyze the absorbed energy was effective on the estimation of impact characteristics of cast irons. (3) The difference in impact energy of the materials collected from different parts of the vessel along the radius direction was not recognized. It was found that the ductile-brittle transition temperature was about 270K. (4) Above the transition temperature, the absorbed energy was dependent on the ferrite grain size, section area rate of the ferrite phase and the ductility of it. Below the transition temperature, graphite nodules were found to arrest the brittle crack propagation.

Key Words:ferritic cast iron, spheroidal graphite, microstructure, FFT process, absorbed energy, ductile and brittle fracture