Abstract
Relationship between the structure of cast irons and the ultrasonic velocity was investigated with the following results :
(1) Ultrasonic velocity V was quite sensitive to the structure of cast iron.
(2) Velocity V was influenced by the graphite structure in that V increased with an increase in spheroidization ratio or graphite shape factor and with a decrease in size, nodule number and area fraction of graphite. Correlation between these factors and V was close when structure and phase ratio of the matrix were kept similar.
(3) V was also influenced by the matrix structure in such a way that V increased with an increase in matrix hardness when graphite structure was kept similar. Various heat treatments to change the matrix resulted in decrease in V as compared with the structure after casting.
(4) Structure of cast iron can be quantitatively assessed by measuring the ultrasonic velocity V, provided that the manufacturing history of the iron is known.
