Koji Kajikawa

Numerical Simulation of Macrosegregation in 570-Ton Low-Alloyed Steel Ingot

We developed a numerical analysis code for macrosegregation in large ingots of Fe-C based multi-component alloys. A numerical simulation of macrosegregation in a 570-ton low-alloyed steel ingot was performed using the developed code in 2-dimensional axisymmetric coordinates. The calculated segregation pattern was compared to the macrostructure of the actual ingot to verify the practical effectiveness of the developed code. A solidification-microsegregation model that takes into account both the equilibrium redistribution of carbon and the non-equilibrium redistribution of other elements was formulated and used in this simulation. In the simulation, numerous inverted V segregations formed as was observed in the longitudinal macrostructure of the actual ingot. The computed carbon profile along the centerline of the ingot presents a similar tendency to that of the actual measurement value. The developed code can be applied to the prediction of macrosegregation in large steel ingots.

Effect of Solidification Front Angle on Freckle Formation in Alloy 625

Freckle formation depends on solidification front angle in ingots. Freckles can be divided into two types; one is a solute-enriched liquid trail growing upward and the other is a solute enriched liquid trail growing downward. The effect of solidification front angle on upward type freckling alloy was reported by Sakurai et al. However there are few studies on the effect on downward type freckling alloys. In this study, the effect of solidification front angle on freckle formation was investigated using downward type freckling Alloy 625. Although freckle becomes difficult with decrease in the solidification front angle as expected, the effect on its solidification front angle was larger than that on upward type alloy A286. It is suggested that the difference is due to the freckle formation mechanism