高強度・高靱性球状黒鉛鋳鉄の疲労信頼性に関する基礎的研究 : 第1報, 軸荷重疲労限度に及ぼす基地組織の影響に関するフラクトグラフィ的研究

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In order to estimate and improve the fatigue reliability of spheroidal graphite iron (SGI) with high tension and toughness, the influence of the matrix structure on the fatigue limit was examined through fractography, with a special focus on austempered ductile iron (ADI) with the bainitic ferrite-retained austenite dual structure. Under the fatigue test of tension-tension loading, R=0.05, it was found that ADI is superior to the SGI with all-pearlite matrix in terms of the fatigue limit and also the ratio of fatigue limit/tensile strength. The fractography showed the fatigue crack initiated at the microporosity in both of the above mentioned SGIs with the matrix structure of high tension. Therefore, it could be understood that bainitic ferrite-retained austenite dual structures had lower notch sensitivity to the microporosity of casting defects than the full pearlite matrix.
1992-11-25