CONTROL OF CHANNEL SEGREGATION IN CAST STEEL - A REVIEW.

Channel segregation appears as solute-rich lines in the form of 'A' (or 'freckles') and 'V' patterns in the finally solidified alloy and originates in the liquid plus solid mushy zone during the solidification process. Research on the formation of channel segregation has been conducted for the past half century but considerable progress has been made in the last decade in more clearly elucidating the responsible mechanisms. The major controlling feature appears to be in decreasing or eliminating the fluid flow along the interdendritic channels in the mushy zone. In this respect the composition of the alloy to be cast and the thermal conditions during solidification play a dominant role. This paper provides practical guidelines for decreasing the extent of channel segregates in cast steel components based on the recent mechanistic research conducted, particularly in Japan and the U. S. A. (Edited author abstract. )