INVESTIGATION ON THE ORIGIN OF SOME TYPICAL IN-MOLD CASTING DEFECTS.

The origin of two types of surface cavities, as well as two types of shrinkage related cavities, typical of high productivity automotive ductile iron castings produced by the in-the-mold process, is elucidated; the remedial measures that resulted in the successful control of these cavities in the plant are reported. An Auger Electron Spectroscopic (AES) study of a number of typical casting cavities in ductile iron treated by the in-the-mold process was carried out. The depth profile of concentration changes was examined, using ion sputtering to remove a known thickness of surface layer at a time. Two types of surface cavities could be distinguished. In one, the enrichment of magnesium was detected using AES near the surface of a large cavity, located at the metal/mold interface, suggesting that the cavity is associated with magnesium vapor. (Edited author abstract. )