フェライト球状黒鉛鋳鉄の衝撃破壊特性に及ぼすけい素量の影響

抄録

  The effects of silicon content and testing temperature on the impact fracture characteristics of ferritic spheroidal graphite cast irons were investigated. V-notched specimens of spheroidal graphite cast irons containing silicon of 2.17 to 7.50 percent were tested by using an instrumented Charpy impact testing machine. The proof stress and tensile strength increase linearly with increasing silicon content in the range of 5 percent or less. Both elongation and reduction of area decrease slightly with increasing silicon content up to 3.5 percent and decline sharply between 4 and 5 percent silicon. The absorbed energy vs. temperature curve shifts to the higher temperature with increasing silicon content. The absorbed energy plotted against silicon content at a given temperature decreases rapidly at a certain critical silicon content, which shifts to the higher silicon side when testing temperature is increased. The fraction of cleavage fracture vs. temperature curve corresponds well to the absorbed energy vs. temperature curve and the energy transition temperature is reasonably consistent with the fracture appearance transition temperature. The ductile-brittle transition temperature rises by about 90 degree C per 1 percent of silicon. The maximum load increases with decreasing testing temperature in the range of ductile fracture and begins to decrease at the fracture transition plastic (FTP) point.