球状黒鉛鋳鉄の強度評価に関する基礎的研究 : 第1報,静的引張性質と基地組織の関係

In order to examine the effect of microstructure on the static tensile properties of a spheroidal graphite (SG) cast iron, eight kinds of materials with the same chemical composition and with a systematically varied microstructure were prepared. After tensile test, Young's modulus E, and the ultimate tensile strength σB and elongation φ of each material wee characterized using several microstructural parameters such as the area fraction of pearlite fP, density ρ and SG state related parameters (area fraction, particle number, sheroidized ratio). The results obtained are summarized as follows : (1) The relationship between E and an applied stress σ showed a trend which supports the presence of load transmissibility of SG. (2) The base microstructure and SG induced changes of E, σB and φ which were well characterized by the parameter fP or ρ. For materials with a higher fP, the tensile properties were primarily dominated by pearlite, and SG had less effect. (3) In the ferrite-base material, SG affected the values of σB and φ. Those effects were evaluated by parameters relevant to the SG state.