Modeling transport phenomena during electroslag remelting of alloy 625.

摘要

A numerical model is used to examine the transport phenomena during Electroslag Remelting (ESR), primarily the phenomenon of macrosegregation. Another model has been developed to study morphological effects on macrosegregation during the ESR process, including grain growth kinetics and solid grain movement. Both models are built on an existing model that is capable of solving mass, momentum, species, and energy conservation equations during multicomponent solidification.;ESR is a secondary melting process used to enhance the metallurgical structure and refine the chemistry of an ingot. ESR consists of passing an alternating current through a consumable electrode immersed in an electrically resistive slag that generates enough heat to melt the electrode. There are limitations for ESR due to an increase in segregation levels with ingot diameter. In order to produce larger ingots than current practice, several constant current ESR runs are simulated to explain possible ways to minimize the segregation levels. Low currents are found to decrease the segregation level as well as shifting the initial composition to decrease the solutal buoyancy force.;The columnar-to-equiaxed transition model is used to examine the effect of having free-floating equiaxed grains in the center of a casting. The CET is shifted by changing the thermal boundary conditions, the free-floating equiaxed particle diameter, and the possible number of heterogeneous nucleation sites. Comparisons are drawn between the static castings of the CET model and the ESR ingots.