Bending Characteristics of Blasted Ferritic Spheroidal Graphite Cast Iron

Bending properties of cast iron are considered to be affected by work hardening and residual stress formation in the surface layer caused by blasting to remove molding sand from the casting surface. However, the influence of the blasting on the bending properties of cast iron have yet to be investigated and very few studies have been performed on residual stress distribution in the blasted surface layer. In this present work, the residual stress distribution in a shot blasted surface layer of ferritic spheroidal graphite cast iron and the bending properties were investigated. The surface was work hardened up to 260∼290 Hv from 200 Hv by blasting and a deeper work hardened region was formed by the blasting with increasing shot size. Shot blast caused compressed residual stress in the surface layer and the maximum residual stress value was more or less the same for different shot sizes. The residual stress distributed region corresponded with the work hardened region and the region deepened with the increase of the shot size. Fractured bending deflection was very small after blasting but the bending deflection was restored to the non-blasted state by stress relief annealing.