Abstract
Feeding behavior in the processes of unidirectional and cylindrical solidification of Al-3mass%Si alloy ingots was examined by measuring the change in height of a hot top. A method for accurately measuring the surface fluctuation of the hot top was devised by the authors. The surface of the hot top starts to fall rapidly as the molten metal at the bottom of the mold initiates to solidify. The fall is suppressed immediately after the top of the ingot reaches the temperature corresponding to the fraction solid of 0.67.
Densities of liquid and solid necessary for the analysis of the feed behavior were determined. The ingot was partitioned into minute volume elements for the analysis, and “ feed components ” were evaluated in the range from liquid state to solid state via liquid-solid transformation, from the density change with the lapse of time after pouring. Feeding consists of the following components for compensation of contraction ; thermal contraction in the complete liquid and complete solid, solidification contraction below and above the fraction solid of 0.67, and thermal contraction of the hot top. The value of 0.67 is the limit of feeding possibility. A comparison of the feeding curve obtained by summing the quantities of those components and measured one shows a good agreement in the range of the feed.
