AFS Library

CONTROLLING ALUMINUM GAS POROSITY

20072121
Journal: Modern Casting V 96 N 1 P 46, Jan 2006 (1 p)
Author: AFS Technical Department

Molten aluminum is vulnerable to picking up hydrogen and at solidification this hydrogen is released forming gas porosity in the casting. The primary source for hydrogen is water vapor. A graph shows the very good correlation between humidity and casting scrap, with the months of May-August being the major problem months. Good foundry practice dictates the avoidance of all conventional moisture sources. However, ultimately, degassing of the molten aluminum is often the required practice needed to produce quality castings. This is accomplished with a rotary degassing device in conjunction with a purge gas. The easily conducted reduced pressure test (RPT) can be used to evaluate the condition of the molten aluminum on the shop floor.



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