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Article: RPT measures hydrogen gas, effects on casting quality. (Reduced Pressure Testing, part 2)
- Article from:
- Modern Casting
- Article date:
- April 1, 1992
- Author:
CopyrightCOPYRIGHT 1992 American Foundry Society, Inc. This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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This vacuum test is a good evaluator of hydrogen gas presence and subsequent cast metal porosity in an aluminum alloy melt.
It is well known that liquids absorb gases as illustrated by the carbon dioxide contained in a bottle of beer. Similarly, liquid aluminum has a high affinity for hydrogen gas, entrapping it in the form of internal pores and surface blisters when the metal solidifies. Too much hydrogen in aluminum can seriously degrade the casting quality.
The principal source of contaminating hydrogen is from water vapor or steam present in the atmosphere in and surrounding the furnace. Moisture is present in refractories, scrap and a host of other ...