Effect of Notch and Grain Size on the Fatigue Strength of Cast Stainless Steel.

Rotating bending fatigue tests were carried out on the notched specimens of cast stainless steels. We prepared fine and coarse grain size materials in order to investigate the effect of grain size on the notched fatigue strength. The main results are summarized as follows : (1) The notch radii of the branch point ρ0 are nearly 0.3 mm, independent of grain size. (2) The master curves of Ktσw2 vs 1/ρ of the two materials are nearly equal, but the master curve of Ktσw1 vs 1/ρ of fine-grain-size material is somewhat higher than that of coarse-grain-size material. (3) When the notch radius is larger than about 2.5 mm, the notched fatigue strength of cast stainless steels decreases by the effect of a microshrinkage cavity.