The purpose of this study was to elucidate the static tensile, high cycle fatigue, and impact properties of solution-strengthened ferritic ductile cast iron (SSFDI) compared with traditional ferrite-pearlite type ductile cast iron (FCD) of similar strength. 500MPa and 600MPa classes of SSFDI and FCD were prepared by adjusting the chemical composition of melts. Tensile tests were carried out based on JIS Z2201, which revealed that SSFDI500 and SSFDI600 possessed higher 0.2% proof strength, higher elongation, and reduction of area than FCD500 and FCD600, respectively. Fatigue test was performed with an Ono type rotating bending test machine. The fatigue limits of SSFDI500 and SSFDI600 were 298MPa and 318MPa, which were about 10% higher than those of FCD500 and FCD600. The fatigue crack initiated at defects such as micro-porosity and abnormal large graphite. The cyclic number to the crack initiation was higher and also the crack propagation rate was lower in SSFDI. Charpy impact tests were carried out on V-notched, U-notched, and unnotched test pieces of SSFID500 and FCD500. The fracture appearance transition temperature (TrS50) of V-notched SSFID500 and FCD500 was 69℃ and －11℃, respectively. TrS50 became higher with the increase in Si content and the pearlite ratio of matrix. Compared with pearlitic FCD700, SSFID500 with 3.8%Si showed higher impact energy (E) above 40℃ and similar E values at lower temperature. Transition temperature was lower and the upper shelf energy was higher in the order of unnotched, U-notched, and V-notched specimens. As the transition temperature and upper shelf energy of SSFDI were higher than those of FCD, E-temperature curve of SSFID500 intersected the curve for FCD500. The intersection temperatures for V-notched, U-notched, and unnotched specimens were 67℃, 60℃, and 11℃, respectively.
