Three-dimensional Numerical Simulation of Channel Segregation in Directionally Solidified Sn-20 mass% Bi Ingot

Abstract

緒言 ・及川 勝成2) ＊ ・安斎 浩一2)Three-dimensional Numerical Simulation of Channel Segregation in Directionally Solidified Sn-20 mass% Bi IngotTomoki Sawada, Katsunari Oikawa and Koichi anzai Synopsis : Channel segregation behavior of a lateral directional Sn-20mass%Bi ingots was examined by X-ray computing tomography (X-ray CT) and three-dimensional numerical analysis. The channel segregation with string shape from near the cold wall side was observed by the X-ray CT and those segregation patterns could be reproduced by the numerical analysis. Low concentration regions also appeared above the channel segregation in both X-ray CT images and numerical analysis results. These results suggest that the proposed numerical method is a reasonable model to simulate the channel segregation. Detailed investigation of the effects of convection on the generation of channel segregation showed that a solidification-accelerated region (SA-region) and solidification-retarded region (SR-region) were formed by the fluid flow. At the SA-region, solidification was accelerated by the inflow of lower Bi concentrated liquid. On the other hand, in the SR-region, solidification was retarded by the inflow of the liquid with high Bi concentration from the SA-region. It was found that the SA-region (called donor part) and SR-region (called acceptor part) group into pairs, and generate the channel segregation.

Inclusion flotation-driven channel segregation in solidifying steels

“… 27 ), Sn-20 wt.%Bi (ref. 28 ), and so on.) and even a few special steels (that is, high Si steels 29 ).…”

Macrosegregation simulation model based on Lattice-Boltzmann method with high computational efficiency

“…Refs. [17][18][19], it is important to develop the LBM-coupled model equivalent to the other NS-based models that include effects of solid fraction in different ways. In this regard, the full volume-averaged Navier-Stokes equation can be reproduced by LBM developed in Ref.…”

“…In this study, the LBM-coupled model is constructed by coupling the MLBK method with the solute and energy conservation equations. As is similar to the previous work, the present modeling rests on a NS-based model developed in early studies [17][18][19], which was chosen because the numerical implementation is relatively straightforward and the simulation results for lateral directional solidification of Sn-Bi alloy and continuous casting of steel were already reported [17][18][19].…”

“…Equations 1and (2) are coupled with the following energy conservation and solute conservation equations [17][18][19]…”

“…given as a function of Bi composition and also the partition coefficient was given as a function of temperature as described in in Ref. [18]. In this calculation, β in Eqs.…”