Effects of Casting Skin Roughness on Static and Fatigue Strength in Spheroidal Graphite Cast Iron

Tensile test and fatigue tests under cyclic tensile load and cyclic rotating-bending load were conducted on several spheroidal graphite (SG) cast irons with casting skin, and the following results were obtained. The tensile strength, elongation and fatigue strength of SG cast iron with casting surfaces are considerably smaller than those of iron with machined surface, and decreases as skin roughness becomes larger. This tendency is due mainly to stress concentration generated from the roughness of the casting skin. Fatigue strength under cyclic rotating-bending load is affected to a greater extent by surface roughness than under cyclic tensile load.