鍛造用鋼塊に生成する逆V偏析の発生状況と影響因子

抄録

Since "A" segregation in forging ingots has adverse effects on the quality of products, it is important to determine quantitatively the number, the size, and the extent of segregation of "A" segregation in ingots. For this purpose eleven commercial ingots of different sizes and steel grades were examined. The results show that "A" segregation spots distribute in a region surrounded by two coaxial circles and that the peak of the number of spots is around the center of the region, in the cross section of ingots. The increase in the number from the outer circle toward the peak is determined by the size of the dendrite, and the decrease from the peak toward the inner circle is determined by the decrease in liquid fraction at the ingot center while it is solidifying. The size of the spots tends to increase with increasing the size of ingot and is proved to be dependent of the coarseness of the dendrites. Finally the enrichment of solute in "A" segregation is found to differ among elements and also with steel grades. It is proved that the enrichment is determined by the patition ratio of each alloying element and by the coarseness of dendritic structure.