The solidification characteristics and the macrosegregation of the unidirectionally solidified ingots weighing 2 70t have been examined.
It has been found that neither secondary shrinkage pipes nor V-segregation exist in the ingots and inverse V-segregation exist only in the restricted area near the side wall.
It has been proved that the unidirectionally solidified ingots show the superior nature with respect to the soundness and homogeneity and are very suitable for production of heavy gauge plates by rolling without forging. The reason for the above is supposed that the liquid steel can be fed to the solidification front easily until the final stage of solidification.
The formation mechanism of positive segregation layer beneath the top surface of the ingot has been investigated. It is found that this is formed as the result of inverse V-segregation formation near the mold wall. Based on the formation mechanism, several operational factors to minimize the positive segregation have been pointed out.
