,Numerical Analysis on Columnar-to-equiaxed Transition of delta-Ferrite Dendrite in Carbon Steel Induced by Titanium Carbonitride Particles

Dendrite growth simulations have been performed to analyze Columnar-to-Equiaxed Transition (CET) of delta-ferrite dendrite structure triggered by fine particles of a primary Ti(C, N) crystal. The CET position estimated by Hunt's criterion and the present simulation indicated that the existence of a large number of the Ti(C, N) particles gives rise to the CET of the dendrite structure even in the vicinity of the mold wall under the present casting condition. Furthermore, the capability of the Ti(C, N) leading to the CET was discussed in the light of the different number of Ti(C, N) particles and the different thickness of cast ingot. It was shown that a sufficient number of Ti(C, N) leads to the formation of fully equiaxed dendrite structure irrespective of the ingot thickness.