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Subject: Re: Camshaft porosity
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Date: 05/07/02 at 9:41 PM
Posted by: M
In Reply to: Camshaft porosity posted by Mark Herbert on 03/20/02 at 5:25 PM:
There could be several reasons.
I would evaluate first the H2 content in your aluminum (are you degasing? how much stirring is there during melting?)
Than, since the porosity is located on or just under the surface I would look at the sand composition, compaction density/porosity.
Anyway without seeing the parts and your operation is hard to tell.
It sounds like either the gasses can not escape in time from the metal before solidifies (the metal makes a skin too fast) or because the sand mold is not porous enough.
A mold metal reaction (too high pouring temperature) is less likely in Al alloys.
Chemistry is not the only factor that determines a good pour.
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