Question about the new sand mix at the Toledo plant

Last week at the Toledo plant, they switched to a new green sand mix with a different binder ratio. We had three castings in a row come out with bad surface finish, like the sand was too hard and wouldn't vent right. What binder percentages are you all running for gray iron these days to avoid that?

3 comments

3 Comments

kimblack22h ago

Ugh, that's the worst. We had the same thing happen after a supplier change. Our sweet spot for gray iron is 1.2% seacoal and 5.5% bentonite, water around 3%. Anything over 6% bentonite and our molds get way too hard, the gas can't get out and you get that scabby finish. Did they bump the clay without adjusting the water?

charlesschmidt19h ago

Totally agree, that scabby finish is a dead giveaway. Ran into the same mess last year when our new guy got overzealous with the clay addition. Pushed bentonite to like 6.2% and the molds were like concrete. Had blowouts and scabs all over the place until we dialed it back and got the water right. Your numbers sound spot on for keeping things breathing right.

jamesc7916h ago

Interesting how different shops can be. Our system runs best with a bit more clay, around 6.8% bentonite, but we also use a much finer grain sand. That extra clay helps us hold detail on complex parts without the scabs, as long as the mulling time is right to keep it from getting too dense.