The Shop > Metal Stuff
Oil fired crucible furnace
vtsteam:
Russell, thanks so much! I sometimes wonder if it isn't boring or irritating to people for me to keep going onand on with examples of bad castings. I sometimes think I ought to wait until I can post things that work out, and save all the long list of mistakes and problem pours. But hell, John Doubleboost shows us what really goes on when you try new things, and I enjoy, and learn from that part of his videos.
So I figured just keep posting this crap as it happens, until you get a good casting, Steve. Or just finally give up! Which I have to admit sometimes crosses my mind. Particularly when I open one up that I'm sure went well, and see a bigger hole than I had before, or a bunch of slag! Seems like when that happens, the next day, I'm up for it again, and think, "Wait, maybe if i just do this .......this time for sure...."
Anyway thank you Russell -- you all make it worthwhile.
:nrocks:
andyf:
--- Quote from: vtsteam on July 26, 2013, 12:46:47 PM ---Russell, thanks so much! I sometimes wonder if it isn't boring or irritating to people for me to keep going on and on with examples of bad castings. I sometimes think I ought to wait until I can post things that work out, and save all the long list of mistakes and problem pours.
--- End quote ---
Though I'll never start casting iron myself, it's still very interesting watching you climb the learning curve (or cliff). Anyhow, if you only posted perfect pours, no-one would really know what you did to get rid of the earlier imperfections.
Andy
vtsteam:
Thank you Andy! I'm glad it's still interesting to people.
It rained today, but I did take the opportunity to take a 50 gram sample of my sand and dry it in a 200F oven for a half hour and re-weigh it. Seems I lost 2 grams, so that works out to 4% moisture content.
The sample was on what I would think of as the dry side, by feel to start with. So this gives me a rough reference to what 4% water is like.
Probably I should repeat that with 200 grams to get a more accurate read -- might do that tomorrow. Then I could gradually add measured amounts of water to the dried sand to get 3 through 6 percent moisture samples. This will help me a lot because I'm not used to the feel of bentonite tempered greensand.
I can say that for several of the early pours and a few of the later ones the moisture content was higher than 4%. So that was probably part of the problem with blow holes.
awemawson:
4% is what I aimed for for both aluminium and cast iron and it seemed to be ok
vtsteam:
Thanks Andrew -- ironman also shows 4% in his mix.
Unfortunately my test yesterday seems off. I was thinking, my digital scale only reads to 1 gram, and with a 50 gram sample +- 1 gram is the same as +- 2%. So it could have meant I had anywhere from 2% moisture to 6% moisture. Not necessarily 4%.
So I repeated it this morning, this time with a 200 gram sample. And I got 195 grams after drying. Which is 2.5% +- 0.5%.
So yes, the sand is a little on the dry side for me by feel, and by actuality.
But that shouldn't hurt permeability I would think, and as long as the mold holds together, I would think it's a positive.
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