減圧処理による片状黒鉛鋳鉄の組織に及ぼす酸素の影響

抄録

  In order to clarify the effects of oxygen on graphitization in cast iron, various pig irons were melted in air and held for various duration under vacuum ranging from 1 Torr to 5 Torr at 1773 K to 1823 K. Molten iron was cast into green sand mould in air, and round bar specimens were made. Fractures and microstructures of round bar affected by oxygen were studied.
  The total oxygen and that dissolved in molten iron were measured. In the first stage of the decompression process, the dissolved oxygen content had a tendency to increase slightly, and decreased as low as 2 massppm afterwards. As the processing time increases, the flake graphite structure changed from type A (or type D plus chill structure) to an increase in the chill structure to inverse chill, and finally to the type D graphite structure (without chill). The molten iron of D which was held for 30 minutes under low pressure was added with 3% Fe-Si-Ca for inoculation. The graphite in irons spheroidized easily.