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Pro tip: watch the pour temp on big molds, a job in Toledo taught me that.
We rushed a 500-pound casting for a pump housing and the metal was too cold, ended up with a massive shrink cavity right in the thick section. Anyone got a good rule of thumb for gray iron in heavy wall castings?
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angelaellis3mo ago
My buddy had a similar mess with a big gear blank... they were pushing to get it done before a holiday shutdown. The metal looked good in the ladle but the mold was huge and cold, just sucked the heat right out. Ended up with a sink you could fit your fist into, dead center of the web. They learned real quick to add a good 50 degrees over their usual temp for anything over a couple inches thick.
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Overstating it a bit, don't you think? A 500 pound casting with a shrink cavity is a headache but it's not the end of the world. You grind it out, weld it up, and move on. Plus I've seen guys pour a full 100 degrees over spec and still get porosity if the mold sand is too wet. @angelaellis's buddy probably had other issues too, not just the pour temp. Grey iron's forgiving enough that a simple 50 degree bump isn't some magic bullet for heavy sections.
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