Speaker
Description
Partition coefficients are key parameters to predict compositional segregation in large steel ingots. The random sampling method combined with mass-balance analysis or Scheil-Gulliver’s equation has been widely used to determine partition coefficients. However, these approaches have mainly focused on steels exhibiting single-phase solidification, and no reports have been found that address Fe‑based alloys involving a peritectic reaction that changes the solid phase during solidification. In this study, an experimental method accounting for changes in partition coefficients associated with the peritectic reaction was developed by combining random sampling method, mass-balance analysis, and unidirectional solidification.
A low‑alloy steel exhibiting the peritectic reaction was used. The specimen was unidirectionally solidified upward in a resistance‑heating furnace and quenched during solidification. Two regions on a vertical cross‑section were sampled before and after the onset of the peritectic reaction, exhibiting ferritic and austenitic solidification, respectively. Solute concentration distributions of Mn, Ni, Cr, Mo and V were obtained using an electron probe microanalyzer (EPMA). Random sampling was applied to determine solute concentration profiles, and partition coefficients for each element were calculated through mass-balance analysis.
The partition coefficients of Mn and Cr showed no significant change across the peritectic reaction. In contrast, those of Mo and V decreased, while that of Ni increased after the reaction. These variations were attributed to changes in the solidification phase induced by the peritectic reaction. The partition coefficients obtained by the proposed method showed slight deviations from equilibrium values due to back diffusion. Solidification simulations of compositional segregation using the determined partition coefficients showed good agreement with the segregation in an actual steel ingot.
| Speaker Company/University | The Japan Steel Works, Ltd. |
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