The Effect of Fluid Flow on the Macrosegregation in Steel Ingot

Abstract

It is possible to show quantitatively the macrosegregation in steel ingot if the flow velocity of bulk liquid during solidification can be obtained. It is found that the flow velocity of bulk liquid is determined by applying the hydrodynamical method known as Taylor's vortex flow to the solidification. Using this method, the following relation is introduced, U/V=7500Sh/(1-Sh) where U is the How velocity, V the solidification rate, and Shthe fraction of solid depending on the washed depth. The effective distribution coefficiemt, ke is theoretically deduced on the basis of the mass transferwith turbulent mixing in the solidifying zone, which is composed of solid and liquid. It is expressed as follows:ke=1-Bl/L(1-K0)(1-Sh) U/Vwhere B is an expaimental constant of 0.81×10-2, hhe primary dendrite arm spacing, L the thickness of the solidifying zone, and k0 the equilibium distributioncoefficient. There is a limit fbr the degree of washing against the solidifying zone because of the growimg dendritc morphology, and the limiting fraction of solid is about 0.67. Furthermore the relatiGn among the deflection angle of dendrite, the solidiflcation rate, and the How velocity Gf bulk liquid is obtained.