Analysis of solidification behaviour of low alloy steel ingot casting - simulation and experimental validation

Solidification in a small experimental steel ingot casting was studied using finite element based simulation. Using the model, the phenomenon associated with fluid flow, temperature distribution, mushy zone formation, thermal gradient ahead of solidification front, local solidification time at various instances of solidification was examined. The heat transfer was found significant till a critical thickness of the solidified ingot. Air gap analysis during the solidification showed that, in spite of high ferrostatic pressure of liquid metal there is notable air gap in the ingot bottom. The model predicted the final piping shrinkage and some small zones of axial porosity formation. The experimental ingot showed a good match on piping shrinkage and porosity obtained from simulation. The microstructure formation in the experimental ingot could be correlated with simulation results. The approximate regime of columnar to equiaxed transition was estimated form the simulation and was matched with that obtained in the actual experimental ingot. The microstructures of the ingot at typical zones were examined in the ingot and correlated to local solidification time.