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Aluminum melting
unfy:
Welp... next melt after the pic had a blow out. I really should start to go with my gut feeling on if the crucible is fine or not.
Everything is cooling down atm. I'll note that after I decided the crucible was failed - poured out the contents into 2 mini muffins. Started picking charcoal out of the furnace. Even after 10min of killing the oxygen and leaving it open and having removed a bunch of charcoal, the AL inside was still molten. Which means as a furnace material, the PoP and sand is doing okay for AL. Oh, and the mini muffins were glowing red / stayed molten for a long time too. Soooo yeah, that thing was hot.
Will wire brush and take more pics later... but an initial glance seems to show a hole opposite of the eyelet in the wall of the crucible.
Taking shooter up on his offer to look for a crucible seems to be the logical next step. Might look on ebay for chinese crucibles / tongs as well.
Will also eye ball propane furnace builds with more proper clay etc. Charcoal has been great as experimentation, but I'd like to move on to something cleaner as well as easier. add: consistent
Some other thoughts: did the charcoal get way too hot ? I know folks say propane gets hotter, but when it's "gettin it", charcoal seems to really be abusive heh. I have done some "gently scrape the sides with stainless steel spoon" stuff as part of getting rid of dross/slag. Is it possible that I'm taking crucible material with it when I do this ? I know steel crucibles will flake with AL temps and contaminate the AL - is it possible that even though I'm not putting any pressure on the wall when doing my scrape, that I'm making it worse ?
To repeat last post: eyelet is ****ing awesome for pouring etc.
To repeat a comment earilier: the offset air tube for swirl flame action is awesome.
I'll be doing more tomorrow.
Even though you're wearing welding gloves, be aware that if you cook them, they'll get hard / rigid. Especially at the seams. I've now cooked 1.5 "right hand" gloves heh.
First pic below shows a crack that has developed in this 'new second lid'. Everything seems fine, though. Not entire sure what that thing line originating from the bottom is. I'll eye ball things more later. Lastly - the U bolts have started do discolor. Different gloves ? heat ? I dunno.
Second pic shows the crack as well , but more importantly a peak down into the chamber. There's a jet of slightly yellow flame roaring out the vent hole that you can't really see. The "laser" looking things would be flying embers. The crucible was probably already failed in this pic, btw.
edit: forgot to attach pics
unfy:
Been melting more today.
The changes:
* well, the lid broke cleanly in half when i lifted it this afternoon before getting started. since it's a clean break with no other cracks, i'm still using it.
* using a chunk of fire brick as a plinth beneath the crucible (score and break kinda like glass or plexi ... it does but doesnt work lol)
* when removing dross / slag, i'm only digging straight down into the crucible, avoiding the sides.
* on my second melt, I just kept adding cans, letting them stack without caring too much. did one clean and then just stacking them again. furnace and crucible all had that nice red glow so i just kept stacking. I'd gently push the cans down into the crucible to keep making room. Particularly, i'd try to take my crushed cans in a <> shape and push them spikey end down. Avoids the wall and I can stop before getting too far down. Towards the end, a nice pool of AL was formed and I was able to more or less just push cans into the pool repeatedly (much like dealing with molten lead and feeding small ingots).
* dumping the second melt, there was a whole bunch of crud at the bottom of the crucible ... on the reheat i'll clean it up a little bit, but not much.
Pics later.
shooter:
it sounds like you are taking what you are using for a pot out and pouring it into the molds, ever think of using a ladle and dipping it out? I would think that disturbing everything to take it out might be hard on stuff
unfy:
I don't doubt that the thermal changes are prolly causing problems.
Using a ladle is probably not really gonna work. While lead has a high specific heat / density - aluminum cools so quickly that it's just not likely to really work. That said, does the stainless spoon I use end up glowing red ? Yes. The little bit of flat stock I use for poking / skimming ? Yes. Could heating the ladle to red hot possibly help ? Maybe. I really don't care to try to ladle 1400F liquid, though.
Coworker wants to try slitting the exhaust pipe down the middle and wrapping it around another section of pipe. I dunno if it's really gonna help, but it might... so why not.
Charcoal touching the crucible probably aint helping. Using really dirty / crummy cans probably aint helping. The slag/dross/whatever-the-****-its-called does like to create a jellied sponge like material. This will stick to itself and to the crucible walls. Who knows how many layers of crucible flakes off with it when you break it off a little bit etc.
Don't have much on pics. Just gonna show the cracked lid after it was used. I'll make another lid some time this week. I'll include some wire mesh this time to see if it helps with strength.
Crucible failure was along the walls again.
Using a plinth seems to have really helped. The stable base for the crucible while the charcoal crumbles is alright. Due to the refactory and such of the furnace - there's also not a concern about applying direct heat to the bottom of the crucible like the double coffee can furnace. This also means the base of the crucible isn't necessarily swimming in charcoal dust as time drags on. The stable base means it aint leaning to one side and all of that jazz.
After each melt, you really wanna take the big burning chunks of charcoal out (and save) and dump all the dust / sand charcoal. Then repopulate the furnace with old hot charcoal and throw more on top of it. Billows / air powered charcoal does burn quickly :).
Expect a 'normal large' bag of charcoal to last 2, maybe 3 melts. At least, when doing cans.
So far, doing cans has been interesting as a learning experience. I really don't suggest doing it as a full time source of AL though. It's so dirty... such a hassle, etc.
Oh, Sunday's melts yielded a little over 2.5lbs of aluminum, including the puddle recovered from the bottom of the furnace after failure.
I've got almost everything to build a rammed up / harder furnace. As in something for propane usage. Gonna double check some dimension suggestions and buy some air ducting for the outside shell. Yes, air ducting as a crucible or anything inside the furnace is bad because of zinc fumes, but with enough refactory the outside doesn't get that hot.
When I do that build, I'll keep pictures posted here.
Charcoal has been great as a 'get your toes wet', but I'm ready to move on. So yes, I do suggest the pail furnace as a first go.
That lid picture ... actually... it won't let me upload it. Or ... will it ? Forum is hating me atm...
unfy:
It'll be time to try this again.
I've been saving up diet soda cans over the winter, etc heh.
I have the materials to build a "more proper" furnace from last fall. Just need to decide on final dimensions. This will be a propane fired furnace.
Crucible is still a curious question.
Graphite crucibles aren't terribly expensive from, say, eBay (even those in the USA etc).
I've found slightly better prices on steel pipe, but still nothing "great" for casual tinkering.
I have grabbed the cheap $70-$80 flux core wire welder from horror freight - as well as parts needed to turn it into a DCEN welder instead of AC. Final piece arrived today - so hopefully I can get it converted over the next few days. Note - I'll have to consider myself a complete noob and starting from scratch when it comes to welding heh. Been far too long.
Does the crucible really have to be round ? Sure there's strength to round, but ... ?
Also, when moving to propane, would exhaust pipe actually work out fine ?
blah blah blah blah blah.
I've also been building a cheap CNC machine as a 'toy' ... so ... my time is rather split between work / a bunch of projects heh.
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