抄録
This study aims to clarify the effects of the external notch on the impact and bending characteristics of pearlitic spheroidal graphite cast iron (PDI) and pearlitic compacted vermicular graphite cast iron (PCV). We prepared Charpy-type specimens with five kinds of notches whose stress concentration factors (α) varied from 1.0 (unnotched) to 4.8. These specimens were subjected to the instrumented Charpy impact test in the temperature range between 173 K and 423 K and also to the 3-point bending test with a slow loading speed at room temperature.
The results of the Charpy impact tests and 3-point bending tests indicate that the absorbed energy greatly decreases with an increase in α from 1.0 to 2.3, but decreases only slightly above 2.3 in both samples. When the absorbed energy is divided into the crack-initiation energy and crack-propagation energy, a decrease in the crack-initiation energy mainly accounts for the decrease in the total absorbed energy. In comparison of PDI and PCV, the former is more sensitive to the notches than the later in both testing methods. The impact characteristics are more sensitive to notches than the 3-point bending characteristics in both samples. PDI and PCV show considerably smaller absorbed energy and higher transition temperatures, and have larger sensitivity to the external notch compared with ferritic matrix cast irons.
