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Tried a 90% recycled sand mix for my green sand molds last Tuesday
I ran a test batch using reclaimed sand from our yard mixed with only 10% new silica for a set of pump housings. The molds held shape fine but the surface finish came out rough and pitted on every single casting. Has anyone else had trouble with recycled sand causing porosity issues?
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derek9945mo ago
You mentioned "surface finish came out rough and pitted" and honestly, I used to be one of those guys who swore recycled sand was fine as long as it passed a basic sieve... but then I had a real bad run with some reclaimed stuff from our yard too. The fines buildup was way worse than I thought, and all those tiny clay particles just held moisture in the wrong spots, causing little steam explosions during the pour. It took me three tries to realize the problem wasn't the sand itself but the lack of proper dust collection during the reclamation process. Now I always test the AFS grain fineness and have a blower system to pull out the ultra-fines before even mixing it back in. You might want to check if your reclaimed sand is holding too much dead clay, that was the hidden killer in my setup.
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jana1195mo ago
Derek, it's actually AFS clay content testing you want, not grain fineness.
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thomas.parker5mo ago
My buddy runs a small jobbing shop and he swore by reclaimed sand for years. He had this one job, a pump housing, came out looking like the surface of the moon. Pitted and rough all over. He spent a week trying to tweak his mix, thought it was moisture in the binder. Turned out he had this massive pile of fines just sitting in his reclaimed sand, dead clay from old core washes. He finally ran the AFS clay test and got a number like 15% when he should be under 5%. The stuff was basically mud. He had to dump the whole batch and start over, now he runs it through a simple air classifier before it even hits the mixer. Cost him a grand in wasted material and a week of downtime.
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