The Effect of Fluid Flow on the Formation of the Negative Segregation Zone in Steel Ingots

Synopsis: The influence of the fluid flow induced by an electromagnetic stirrer and the solidification rate on the formation of the negative segregation zone in carbon steel ingots was investigated. The results obtained are summarized as follows. (1) In the region solidified in the presence of the fluid flow, the growth of columnar dendrite is suppressed and the negative segregation of all the solute elements is generated. These tendencies become remarkable when the fluid flow becomes vigorous or when the solidification rate becomes slow. The following relation was obtained experimentally, U/V•...130 Ke=1-4.17x10-2(1-k0) (U/V)0.58 U/V•†130 Ke=0.54 (element C ), 0.86 (element Mn) 0.44 (element P) where Ke is the degree of the negative segregation, U(m/sec) the flow rate of the bulk liquid, V(cm/sec) the solidification rate, and k0 the equilibrium distribution coefficient. (2) The washed depths in the interdendrite generated by the fluid flow were calculated for each elements by the complete mixing model. It was found that the washed depth for each element well agreed with each other and that the washed depth becomes deep when the fluid flow becomes vigorous or when the solidification rate becomes slow. (3) The calculated results showed that the influence of the diffusion of solute elements in the interdendrite along the solidification direction on the calculated washed depth was negligible.