2001 Volume 73 Issue 5 Pages 287-292
Many sleeves of Ni-hard cast iron in practical roll size were made by the centrifugal casting process and the effects of melting and casting conditions on solidification segregation were investigated. Solidification segregation was found to take place due to non-uniform solidification and the degree of segregation was evaluated by the structure parameter (PDII) that represents the non-uniformity of dendrite structures in coarse and fine regions. Solidification segregation did not generate easily when the PDII value was small. The PDII value decreased when the alloys to adjust the chemical composition were added all together before the first melt-down of the charge material, and when the pouring temperature was low. A lower pouring temperature led to the precipitation of fine and uniform dendrite structures near the surface layer. However, the PDII value increased at the boundary region between the fine dendrite layer and the inner regular dendrite structure, and the non-uniform structure appeared there. The vibration of centrifugal casting greatly promoted the non-uniform solidification.
