EFFECTS OF ELASTICITY AND COMPACTNESS OF GRAPHITES ON THE FATIGUE STRENGTH OF SPHEROIDAL GRAPHITE CAST IRON.

Spheroidal graphite cast irons with both (a) as a perfectly cast pearlitic matrix structure and (b) as a predominantly ferritic matrix structure were austenitized, oil-quenched and tempered to the same hardness level. After heat treatment (a) is considered to have graphites compressed by the matrix, and (b) is considered to have graphites existing more loosely. With these samples, fatigue tests were carried out in order to investigate the effects of elasticity and compactness on the fatigue strength of spheoidal graphite cast iron. The following expected results were obtained: (a) had higher fatigue strength than (b) by about 24%, and the hypothesis proposed by the author was confirmed.