The Craftmans Shop > New from Old
Resurrection of a CFEI 100 KVA Induction Furnace
vtsteam:
I have yet to launch a capsule into space built with homemade castings.
Therefore extreme concerns over weight don't apply, and my aluminum castings are multiple magnitudes of degree heavier than absolutely necessary for their intended purpose. It's frankly a pain to cast too thin a piece, and mass and solidity benefits most machine parts I've ever made as well as looking more substantial and aesthetic.
Occasional tiny pinholes requiring a magnifying glass to see in an aluminum casting are not therefore viewed as a problem. Now, I'm all in favor of others taking steps to perfect their casting, don't get me wrong. But I cast (as most other home shop sandcrabs do) with scrap, which is not devoid of corrosion, oil, dirt, or included steel clips (pistons, my favorite source of aluminum always has steel cast right into it). So the concept of avoiding contamination is doomed from the start. Luckily, it doesn't matter -- the contaminant either burns away into carbon dioxide or powdery dross (which actually protects the melt from oxidation), is fished out (clips) or skimmed off (dirt, oxides etc.) before the pour.
I did once put a crucible cap on an iron melt. Didn't seem to make any difference.
vtsteam:
re. caps....I should add, though, I think a cap would make sense on a brass melt to reduce zinc fuming and oxidation.
And I always felt, when melting aluminum in a charcoal furnace, that charcoal pieces which landed on top of the melt protected it from oxidation. Likewise coke on top of ironman's (luckygen1001 on YT) steel-to-cast-iron conversion melt video did likely reduce oxidation.
awemawson:
No I’ve not used crucible covers in this context. (Yes in the lab on small porcelain crucibles): But I do use a ‘cover flux’ - I say I do, it’s really’ ‘ I did’ as I doubt that I still have any left, there may be a tub in the cupboards of the foundry benches, memo to self to look !
awemawson:
As I thought - the cover flux is long gone, but I did manage to unearth some treasures in my search for it:
A wooden 'snap flask' that I made using sash window catches
Several Sand Sieves in different meshes
Another Plate Pattern for brackets
And my Vacuum Pump used for de-gassing lost wax plaster moulds
Along the way I found a cupboard full of all sorts of dangerous chemicals and card board boxes so covered in mould I hate to think what is inside - the cupboard has been against a damp wall for years - must work out a disposal strategy :bugeye:
vtsteam:
All very nice! :thumbup:
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