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Article: The good, the bad and the porous.(CASTING ANSWERS & ADVICE)
- Article from:
- Modern Casting
- Article date:
- November 1, 2006
CopyrightCOPYRIGHT 2006 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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Q We use the visual comparison method to rate sectioned samples for hydrogen level to evaluate solidified reduced pressure samples. But recently, we have had problems where apparently "good" gas samples still allowed our customer to find unacceptable porosity levels upon machining. What could account for the difference in results?
There are several possible causes for the problems you have identified, and they deal with your sampling processes, the way you are performing the reduced pressure test (RPT) and variations in the samples themselves. Improving your current testing technique or implementing newer testing procedures can eliminate those difficulties.
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