Abstract
Spheroidal graphite cast iron ingots containing chunky graphite were made, and ultrasonic measurement was carried out in the spheroidal graphite region and chunky graphite region. The sound velocity was measured at high precision by the sing-around method. The intensity of the bottom echo and scattered wave were analyzed. The sound velocity in the chunky graphite region was about 0.7% lower than that in the spheroidal graphite region, and the bottom echo intensity was about 50% lower. The change in the bottom echo intensity was simulated under simple assumptions to obtain good agreement with the measurement. There were considerable differences in the scattered wave distribution of both regions. These results suggest possibility to detect the chunky graphite region existing in spheroidal graphite cast iron and to evaluate the size of the chunky graphite region nondestructively.
