鍛造用鋼塊に生成する逆V偏析の発生臨界条件

抄録

Quality of forging products is greatly affected by macrosegregations such as "A" segregation which tends to appear in large ingots. From the points of quality control and assurance, therefore, it is important to establish a method to predict formation of "A" segregation in ingots. For this purpose, twelve commerical ingots of different sizes and steel grades are investigated. Further experiments are carried out, by producing "A" segregation in small ingots, to study the effects of alloying elements. The results show that the critical location of the formation of "A" segregation differs with grades of steel. The location is determined not only by the liquid density difference but also by the coarseness of dendrites. In the case of lowalloy steels, secondary dendrite arm spacings have to be as big as 560 micron meters for the formation of the segregation. Meanwhile the vanishing location of the segregation in the center of ingots is determined by the radius of ingot regardless of grades of steel.