The Shop > Metal Stuff

Oil fired crucible furnace

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MetalCaster:
That does look a bit crusty on the one piece.

I only use clean metal to avoid slag problems.
I bought some ground corn cob, and will either be wire brushing my metal, or sand blasting it with corn cob.

I tried using some baking soda and salt with an aluminum pour, but then tried it again without either, and still had good results, but again starting with clean metal.

I have seen others around here use radiators, but I have not had trouble (yet) with just regular gray cast iron as far as being fuid enough to pour.

Those high-temp pyrometers are quite expensive, so I only use one with brass/bronze/aluminum.
For cast iron, it is just sort of a look/feel/time guess unfortunately, but it does get fluid enough to pour.
I can't dilly-dally around though after pulling the crucible out of the furnace, it has to be poured straight away or it will get cold in a hurry.

MetalCaster:
I need to make one of those scapers.

vtsteam:
Today's second pour. The first pour was a mess -- a piece of slag on the outside of the crucible prevented it from seating all the way down in the pouring shank, I didn't notice. About half way through the pour the crucible slipped out of the shank and emptied the remainder on top of the sand -- hence the burn marks in this cope. One more short pour   :doh:

After uttering a few sentiments that would have made doubleboost blush, I re-grouped, dumped the flask in a wheelbarrow, re-loaded the crucible, started the second melt, and rammed up a new mold.

This time instead of the radiator scrap, I used one of my earlier castings, a sprue and an ingot -- figuring these were all clean metal, and much more massive than the other stuff. I hoped for a lot less slag and a good pour. It melted pretty quickly in the hot furnace, and I dumped in about an ounce of crushed oyster shell. This did seem to liquify the slag better. I had a fuller pot of metal, it seemed, too.

When it seemed hot enough I pulled it out scraped the slag -- much less and better behaved, checked the fit in the shank carefully. and poured.

Unfortunately I thought I saw a small bit of slag go in part way through the pour -- I hoped it would be trapped in the well or gates. If I'd had a partner, he (or she) could have held back the slag with a rake. There always seems to be a little bit clinging to some part of the crucible.

Here's what the second pour looked like -- nice and neat. Not like the first!!

vtsteam:
I had enough at the end to pour an ingot -- a bit of slag dropped in when I tipped the crucible all the way here, too.

While waiting for the mold to cool, I broke the ingot in half to look at the grain. Looks good, and uniform gray, except for the bit of slag.

vtsteam:
Breaking out, the bottom of the casting looked good -- graphite blacking was helping some -- also corners were relatively sharp. This time sprue and riser were well filled -- though short, since the cope is only 2" deep.

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