Abstract
Observation of structures, chemical analysis, mechanical testing and ultrasonic measurement were carried out for the evaluation of spheroidal graphite cast iron containing chunky graphite. In the observation of the macro-structure and micro-structure of thick-walled spheroidal graphite cast iron, a region containing a spheroidal graphite structure showed metallic luster and that containing a chunky graphite structure of distributed minute graphite showed pitch-dark. In the chunky graphite region, the carbon content took higher values than that of the spheroidal graphite region. Results of mechanical testing indicated elongation of the test piece containing the chunky graphite to be about 1/5 of the test piece of the spheroidal graphite structure, and the tensile strength of the chunky graphite to be about 70 N/mm2 lower than that of the spheroidal graphite structure. In the ultrasonic measurement, the attenuation in the chunky graphite was larger than that of the spheroidal graphite structure and the ultrasonic velocity of the chunky graphite was lower than that of the spheroidal graphite structure region.
