バーミキュラ,ダクタイル鋳鉄の疲労強度に及ぼす組織・力学因子の役割について

抄録

The fatigue strength of the compacted vermicular cast iron and the nodular cast iron with a ferrite and/or a pearlite matrix was tested under tension-tension loading and their microscopic fatigue fracture processes were examined by SDEM and EDS. Results were as follows: (1) The fatigue limit σ_W was proportional to Vickers hardness H_V. (2) The ratio of σ_W to σ_UTS for the cast iron with a ferrite matrix was larger than that for a pearlite matrix. (3) The nodular cast iron with a pearite matrix had a highest fatigue limit. Futher, finig spheroidal graphite by the metal mold increased the fatigue limit. (4) The change shape of graphite induced the different mechanism of fatigue crack initiation. It could be interpreted that this fact controlled the fatigue limit.