希土類元素を接種した片状黒鉛鋳鉄の黒鉛化と機械的性質

抄録

  Inoculation treatment is used in the production of flake graphite cast iron to promote the graphitization and formation of type A graphite, thus improving its mechanical properties. If there are no inoculation effects or the inoculation effects are small, type D graphite is generated much more easily. Moreover, it is known that the mixed microstructure of type A and type D graphites has reduced tensile strength. Thus inoculation effects vary with the type of inoculant used and amount added.

  In order to seek out the best conditions in inoculation treatment, this research compared the inoculation effects of Ca-Si, La-Si and Ce-Si inoculations from the viewpoint of the cooling curve.

  The results indicated that there is a linear relationship among ΔT (temperature difference between the maximum eutectic temperature and minimum eutectic temperature), total chill depth, and tensile strength. Total chill depth gradually increased with increasing ΔT, while the tensile strength decreased at the same time. However, the relationships among ΔT, total chill depth, and tensile strength varied with different inoculations. At the same ΔT, the tensile strengths of samples added with rare-earth element alloy were always lower than those added with Ca-Si alloy. The results of microstructure observation indicated that the mixed microstructure of type A and D graphites was generated in the samples added with rare-earth element inoculation, and this led to decreased tensile strength.