The Shop > Metal Stuff
Foundry Furnace for the Tiny Shop
awemawson:
I used to use a Zircon wash on ladles I used for aluminium. Warm the ladle over the furnace and paint it on with an old broad paint brush - it flash dries. Same for stirring pokers etc.
This was to prevent iron dissolving into the melt. I've never been happy with the multitude of ferrous 'pipe crucibles' that you see on the web from a metallurgical point of view. I've always used clay / graphite conventional crucibles.
vtsteam:
This is one of those perennial user purpose and style disagreements. I've used a cast iron plumber's pot for all of my aluminum melting career, other than some bigger pours which used a 4" pipe nipple and welded plate bottom.
Here's the deal -- I mainly melt pistons for stock metal. Those pistons were cast with steel clips right in them. So no way are you going to avoid "iron contamination" by using a ceramic crucible or a ladle wash with these. Nor do most of the world's engine makers for what is obviously an extremely demanding application. Melted pistons, despite the steel clips make great castings -- naturally. That's what they are! My castings for my lathe, accessories turbine, etc were fine castings, the lathe hasn't fallen apart after a dozen years, and I expect it to last a lifetime.
Now there is nothng wrong in my opinion with using virgin alloys, a non-ferrous crucible or wash to control a melt and get single named alloy results. If that's what you enjoy doing, and/or you have a demanding application, I don't say no. It suits the application and the style of the caster. And vise versa. If you're melting scrap, and casting heavy sections for non-NASA parts, as most of us do a ferrous crucible isn't a problem and shouldn't be disdained.
What IS a problem is too thin a crucible if steel. It should be at least 1/8" thick and preferably double that to last any time at all. Thin stainless steel canisters burn through in only a couple pours, too. Using a steel soup can is asking for trouble -- not to mention the coatings inhalation problem. The recent video elsewhere on the site using a fire extinguisher bottom, seems both hard to obtain and too thin. Why bother? A pipe nipple is much thicker and readily available. To me the best iron crucible is a cast plumber's pot. It doesn't waste in the flame as steel does -- I've used one for 12 years.
If you are worried about iron, you can line any ferrous crucible on the inside with fireclay and sand if you don't have the bucks for an expensive ladle wash. It will then be a ceramic crucible to all intents and purposes.
vtsteam:
I shoveled snow and chipped away ice until I saw frozen ground then covered with some coarse sand and set-up the furnace. As I mentioned in the Tiny Shop thread temps last night were the lowest of the winter -26C and today it only warmed to 11C and it was windy too. I still wanted to try the furnace out and I used some of my poor grade aluminum and an old lost foam pattern which I'd made last summer for an engine casing. It was only 6mm thick and I'd had some difficulties back then with this gated version of it. But it was something to try with the furnace -- any excuse!
vtsteam:
Gear set out, charcoal lit ready to go. No blast yet Lost foam mold setup in the small orange child's bucket lower left :
vtsteam:
Blast on, coals coming up to heat....4:10 PM :
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