抄録
This is the observation of pin hole defects occurred in cast iron by green sand mold with SEM. All 109 samples (gas hole defects) gathered from 34 foundries are observed. The defects are classified in 4 types as follows : In D), there are still more 3 types defects. A) round pin hole, B) thin & long pin hole, C) fissure pin hole, D) slag pin hole (a : ladle slag, b : inoculant, c : manganese sulfide). Typical SEM photo (A～D) is shown the figure. By standardizing these, SEM photos, it will be possible to classify the pin hole defects occurred in foundries and it will help studying of prevention.
