THE PRODUCTION OF CASTINGS FROM ALUMINUM ALLOYS,
FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OHIO
Pagination or Media Count:
In the solution of solidification problems the difference between the volume of solidified metal and the volume of the crust formed on the channel walls must be taken into account. This difference is attributed to the mech. interaction between the solid and liquid phases in which several solidified metal particles are washed down from the cooled surface. Quantitative appraisal of the difference can be established by the wash-down coefficient K which characterizes the relative rate of the crust growth in the moving metal stream. The coefficient is dimensionless, its values being 0-1. The relation between K and Re, Bi, and N the Reynolds, Biot, and phase-transition nos., resp. was established exptl. by using flows of Zn, Pb, Al and eutectic alloys of Zn-Pb and Al-Cu. Two exptl. methods are outlined to determine K. In the laminar flow regime, the wash-down of the solid phase from the cooled surface is insignificant. In the turbulent regime, the wash-down increases exponentially with Re. With an increase in the ratio N, Bi, K decreases rapidly towards O. At the crystallization temperature, the flow causes a wash-down of the crust which is 5-30 percent of the total metal solidified.
- Fabrication Metallurgy