Study on solidification and macrosegregation of aluminium and titanium in the electroslag remelted ingots of K500 alloy
Xuechi Huang, Kai Du, Yuliang Zhu, Haoran Xu, Zhongqiu Liu, Fang Wang, Baokuan Li, Yingbo Geng
Abstract
This study systematically examines the segregation behavior in Monel K500 ESR ingots, focusing on titanium (Ti)/aluminum (Al) redistribution dynamics. A validated multiphysics model integrating magnetohydrodynamic (MHD) flow, heat transfer, and solute transport is developed, benchmarked against production data to resolve MHD-thermal-solutal interactions under currents of 6300∼8300 A. This model accounts for droplet dynamics, slag-metal interface instability, and the progressive solidification of the ingot. Results reveal vertically stratified distributions of Ti and Al in the metal pool, with solutes progressively accumulating from top to bottom, leading to center-enriched but surface-depleted distributions in solidified ingots. Due to its lower partition coefficient, Ti exhibits 2.7∼3.5-fold higher segregation intensity than Al. Axially, the negative-to-positive segregation transition occurs at ∼60 mm height for Ti versus ∼240 mm for Al, suggesting prioritized solute rejection of Ti at the solidification front. Radially, this transition occurs at ∼150 mm radius for Ti versus ∼65 mm for Al, indicating Ti’s predominant positive segregation and Al’s dominant negative segregation. When the current varies from 6300 A to 8300 A, the metal pool depth rises from 235 mm to 377 mm, intensifying the Ti/Al enrichment and macrosegregation, particularly radial inhomogeneity. The content range expands from 0.067 wt.% to 0.083 wt.% for Ti and from 0.11 wt.% to 0.14 wt.% for Al. Concurrently, the maximum segregation index for Ti increases from 0.1093 to 0.1305, while the minimum value for Al decreases from -0.0305 to -0.0475. Lower currents (e.g., 6300 A) are recommended to mitigate Ti/Al segregation and enhance ingot homogeneity.