鋳鉄の熱疲労

抄録

  The authors have made a thermal fatigue testing equipment which gives a mechanical load on the specimen. The thermal fatigue lives of gray cast iron, ductile cast iron and malleable cast iron were examined under completely restricted and mechanically loaded condition.
  The completely restricted thermal fatigue life of each ductile cast iron and malleable cast iron was longer than that of the gray cast iron. The relationship between strain amplitude (ε_t) and the completely restricted thermal fatigue life (N_f) was expressed by the following equation : ε_t·N_f^α=constant where α was 0.68 in gray cast iron, 0.82 in ductile cast iron and 0.75 in malleable cast iron.
  Thermal fatigue life under mechanical load was shortened with increase in both the heating temperature (T_H) and the mechanical load (σ_M). A T_H-σ_M diagram which shows a given thermal fatigue life (N_f=10³ cycles) was made for each cast iron. At higher σ_M, ductile cast iron and malleable cast iron with pearlitic matrix was resistant to a higher repeated thermal cycle temperature than those of ferritic matrix, but at lower σ_M, the results were reversed.