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Had to choose between a fast pour or a slow one on a big iron casting last week
We were running a 500 pound gear blank and the mold was getting a bit cold. My lead guy wanted to pour fast to beat the chill, but I remembered a tip from a guy in Toledo about slow pouring for less turbulence. We went slow, maybe a 45 second pour instead of 20. The casting came out with way less slag and almost no surface defects. Anyone have a rule of thumb for when to pick speed over a steady pour?
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jason_stone6mo ago
You mentioned the mold was getting cold, which is a real worry. But calling it "chill" might mix up terms a bit. Chill usually means those hard white iron spots from too-fast cooling, not just a cold mold. A slow pour was still the right call to avoid slag. For a big gear like that, I'd pick speed only if we saw the metal starting to freeze in the sprue.
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mary_ramirez676mo ago
Yeah, you're right about the chill mix-up. Seen that white iron happen when the mold was too cold before the pour even started. On those big gears, if the sprue starts to crust over, that's when you gotta pour like your life depends on it.
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laura_white996mo ago
Ever had a sprue freeze up even with a hot mold? Sometimes it's less about the mold temp and more about the metal losing heat in the ladle during a slow setup. A quick pour can save the whole cast if you see that crust forming.
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