I finally got a clean break on that tricky aluminum bronze pour

We kept getting shrinkage porosity in the same spot on a gear blank. Last Thursday, I preheated the mold to 450 degrees instead of our usual 350. I also slowed the pour rate down a bit, filling the sprue slower. The part came out solid, no voids at all. Anyone else tweak their preheat temp for different alloys?

2 comments

2 Comments

victor_carter5115d ago

Yeah, that preheat temp change is huge. I was reading an old foundry manual that said aluminum bronze really needs that extra heat in the mold to fight off shrinkage. It talked about how the slower pour lets the metal feed better into the thicker sections. Your fix lines up exactly with that old school advice. Makes me wonder if our shop is running some molds too cold.

jordant6915d ago

Old foundry manual" makes it sound like gospel, but those books were written for different equipment and alloys. Shrinkage happens, but chasing perfect mold heat sounds like a good way to waste a ton of gas. If the parts are passing inspection now, maybe the cold mold is fine and we're just overthinking it.