1991 Volume 31 Issue 7 Pages 712-720
Sulphide inclusions in HY-80 steels containing sulphur from 50 to 500 ppm especially prepared by resulphurization of commercial HY-80 steels, have been quantitatively characterized with regard to their type, size, shape and distribution using automatic image analysers. The formation of sulphide inclusion in HY-80 steel is discussed from thermodynamic considerations. It is seen that inclusion parameters such as volume fraction and aspect ratio increase linearly with the increase in sulphur content whereas the projected length varies non-linearly as a function of sulphur. The number of inclusion per unit area increases with increase in sulphur content. Correlation of charpy impact energy with these parameters shows that charpy energy decreases with increase in aspect ratio and projected length. The effects of the inclusion parameters on the impact energy are analysed in the light of Bilby's distribution model which unlike the other models, takes into account both volume fraction and aspect ratio of inclusions. The values predicted by the model are found to be in good agreement with the experimental results.