Had to pick between silica sand and olivine sand for a big gray iron pour this week

We had a customer order that needed a really smooth surface finish, and my foreman said I could choose either silica or olivine for the mold. I went with olivine even though it costs about $40 more per ton because I've heard it handles thermal expansion better on complex shapes. The pour went smooth, no veining or cracks on the castings at all. Has anybody else tried switching sand types for specific jobs and seen a big difference?

3 comments

3 Comments

stellachen28d agoTop Commenter

Hold up, did the silica sand give you trouble with dimensional accuracy too on that pump housing, or was it strictly a surface defect thing? I'm curious because the thermal expansion difference might mess with the final shape on something with precise internal passages like that. Always trying to figure out if the extra cost for olivine is just about avoiding cracks or if it actually keeps the geometry tighter too.

averymartin29d ago

You ever had to fight with silica sand on a hot pour and get that weird veining mess? I switched to olivine for a similar reason on a complex pump housing job last year. The silica was causing all kinds of micro-cracks where the metal was thin, but olivine just handled it. It's pricier for sure, but the rework we saved on that single pour easily made up for the extra cost. Haven't used silica on anything with tight tolerances since then.

logan23629d ago

Makes you wonder how many OTHER problems get solved just by swapping the RIGHT basic material first time.