AN INVESTIGATION OF DARK FACET FRACTURE IN CAST STEEL 30MnNiMoCu

A SEM investigation has been made of the occurrence of the dark facet fracture in Al deoxidized cast steel 30MnNiMoCu using dispersive spectrometers of X-ray wave and energy. It was found that the AIN precipitation in the interdendritic areas along the original as-casted columnar grain boundaries contributes mainly to this kind of fracture. The solution and precipitation behaviour of AIN as well as the dependence of AIN on the amounts of Al and Ti added have also been discussed quantitatively.