The effects of side-risers and end-chills on feeding efficiency of plate castings were studied in this research. The solidification cooling parameters were varied substantially by employing various plate thickness and different riser and chill dimensions. The variation of thermal parameters during solidification was obtained by thermal analysis, the porosity content of the castings was measured by Archimedes' method. In addition, the effects of the solidification mode on casting soundness (in terms of porosity) of the A390 aluminum alloy and the relations between feeding efficiency and porosity were discussed.
The results of this study indicate that chills were shown to increase the solidification cooling rates and the temperature gradients established during the eutectic interval of solidification, reduce the width of the mushy zone, increase the time interval available for the transfer of feed metal at the end of solidification and reduce porosity.
The porosity content of the A390 aluminum plate castings increases from the chill end to riser end and decreases with increasing of the riser size.
The effects of the risers together with chills for plate casting were shown to reduce the time of solidification, enlarge the ranges between both the solidification time, increase the feeding efficiency and decrease the porosity content.
Then the thin plate with a small riser, the porosity content raises to an unusually high amount in the middle of the plate castings, because of the rapid of solidification cooling rates and the poor of interdendritic feeding.
Of all the solidification cooling parameters, the extent of casting porosity was found to be correlated with the temperature gradients, freezing index and the feeding efficiency factor.
The casting soundness (decreasing porosity content) in A390 aluminum alloy plate castings is governed by the optimum feeding efficiency of the solidification, the direction solidification conditions and temperature gradients.