Stopping hairline cracks in thin aluminum casts

I've been making small aluminum brackets for a project. The thin edges always get hairline cracks after they cool. I tried changing the sand mix and letting molds dry more. It didn't work. Then I remembered an old caster saying quick cooling causes stress cracks. So, I now bury the molds in dry sand right after pouring. This slows the cooling a lot. Since I started this, the cracks are gone. It's a simple trick that costs nothing. Has anyone else found ways to handle thin sections?

2 comments

2 Comments

karen_west5912h ago

Ever try to chill a casting too fast and get a network of cracks that would make a map look simple? I once got impatient and quenched a thin part, now it sits on my bench as a reminder of what not to do. Your sand trick is clever, just letting everything settle down slowly. I've heard about adding a riser to feed the thin spot, but that sounds like more work than I'm willing to mess up. Sometimes the answer is just to not be in such a hurry, which is advice I clearly need myself.

morganhill11h ago

Indeed, patience pays in the end.