抄録
Density and ultrasonic sound velocity of as-cast, ruptured and heat treated specimens of flaky, CV and spheroidal graphite cast iron were measured and the following results were obtained.
(1) Density and sound velocity were decreased by tensile stress or heat treatment, while they were also affected by chemical composition and matrix structure. Sound velocity was proportional to density. (2) The main reason for the reduction of density and sound velocity was attributed to voids generated in the cast iron during the application of tensile stress or heat treatment. The effect of density upon sound velocity was explained to the most part by graphite content and the amount of voids induced in cast iron. (3) Young's modulus E(kgf/mm2) of cast iron was approximately expressed by the equation (1).
E=21500(Aef−x)+1000(1−Aef)…………………………………………(1)
where Aef is the effective area fraction of the matrix in as-cast state and x is the area fraction of cracks or voids formed by stress or heat treatment. The order of the amount of opening of cracks in ruptured specimens with the same x value was calculated by equation (1) using the measured density and sound velocity as FC20<FC25, 30<CV<FCD45.
