On dry abrasion, the wear resisting properties of the spheroidal graphite cast steel having various matrices which were obtained by different heat-treatments such as normalizing, oil quenching and tempering have been studied. The upper specimens have various heat treated matrices and the lower specimen has the normalizing structure, The results obtained can be summarized as follows : 1. Surface hardness after abrasion showed the difference by each of the matrices, but it had a tendency to attain constant value along with the increase of running distance. 2. Although the surface of specimens was adjusted constant by mechanical finishing before wearing test, surface roughness approached to the characteristic curves in each combination of matrices between upper and lower specimens. 3. The lustrous degenerative layer as seen samples tempered at low temperature was produced by physical factors such as work hardening and tempering effects. 4. On the contrary, the greyish layer as seen on samples tempered at high temperature was very thin and was produced by chemical factors such as oxidizing or nitriding. 5. The upper specimens having much greyish areas did not so much wear the lower specimens, but they showed themselves less wear resisting. On the contrary, the specimens which were covered with lustrous degenerative layer, showed more wear resisting, but the wearing amounts of the lower specimens were increased. Therefore, the combination of the extremely different matrices and the identical matrices must be avoided
