A concise and stable macro segregation simulation model applicable to channel segregation prediction has been proposed. In flow analysis, thermosolutal convection and Darcy's flow were considered. The Darcy term in the momentum equation was stabilized by using the implicit discretization technique. The effect of solute movement at solid/liquid interface was simply formulated by jump condition. With these models, parallel plate flow in porous media problem was analyzed. Results of this stabilized method had excellent agreement with analytical solution and it was shown that the method has good convergence in pressure linear equation. Since time increment is not restricted by Darcy term in the stabilized analysis, the calculation time of the stabilized method was much shorter than the conventional explicit discretization method. For verifying usefulness of the simulation method for macro segregation, the horizontal directional solidification of Sn-10wt%Bi alloy was analyzed and compared with the experimental results by Quillet et al. The regions where channel segregation occurred and tendency of Bi concentration at the bottom of the ingot were found to agree well with the experimental results. The calculation time was as short as and more or less equal to the solidification time in the simulation.

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  Recently, automobile manufacturers adopt high tensile steel for car body production to reduce weight and enhance safety. The manganese (Mn) content in steel scrap however increases as more high tensile steel plates are used. Mn is known as a graphite inhibitor in cast iron, an element that especially decreases the elongation of spheroidal graphite cast iron. Therefore, either diluting the Mn percentage or removing the Mn in the steel sheet scrap is required for using high Mn steel sheet scraps in spheroidal graphite cast iron.
  In this study, for the purpose of increasing high Mn steel scrap recycling efficiency, the method of manufacturing spheroidal graphite cast iron without removing Mn from high Mn steel scrap was examined. It was found that the elongation of the spheroidal graphite cast iron can be increased by adding rare earth element before spheroidizing treatment and adding Fe-Si-Ca-Ba alloy together with spheroidizing treatment.
  These results show that spheroidal graphite cast iron with no more than 1.0%Mn complying with JIS (FCD450-10) standards by adding the rare earth element or Fe-Si-Ca-Ba alloy can be produced. It was also clarified that high Mn steel scrap can be recycled.

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  In aluminum alloy casting, grain refining agents such as titanium, boron, and carbon are widely used to refine and homogenize macrostructures and also improve mechanical properties. However, these grain refining agents may induce serious problems during the recycling stage. In this study, gravity castings with mechanical vibration (0-157 Hz) were conducted and columnar rods (Φ25mm, L210mm) were cast to investigate the effects of mechanical vibration on grain refining, distribution of casting defect, and mechanical properties. Mechanical vibration refined the grains in the middle area of the columnar rods, but the columnar structure remained in their outer region at all vibrational frequencies. The variance of mechanical properties of specimens cast with mechanical vibration became smaller due to the reduction or complete elimination of casting defects in the specimens by mechanical vibration.

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