How not to melt down aluminium cans

[mickulty]

So, some background. I did two years of electrical engineering at university before switching to computer science. As a result, I know a lot of engineers. One of them built himself a furnace for melting down aluminium cans, which we've used a few times with steel crucibles - unfortunately, steel crucibles don't last very long as they get pretty hot and deform easily.

 

Yesterday we went out wombling (collecting bits of litter that could be useful, for non-brits) and got a boxful of crushed aluminium cans which we'd hoped to melt down using a fancy new graphite crucible.

 

Unfortunately the fancy new graphite crucible had been left outside in england, so it was soaked through.

(if you're wondering, I'm holding the camera). Ah well, you live and learn. Fair warning, there's some swearing in the video.

 

I'm still hoping to do my first casting soon, though a new crucible will take a couple of days. The ultimate goal is to make my own VRM/VRAM heatsinks, and hopefully my own (admittedly fairly rubbish if they're aluminium) DICE/LN2 pots as all the commercial ones are really expensive by my standards but I want to move up to apprentice asap after I graduate from rookie league.

 

If anyone's interested I'll happily write up the full process from furnace making to casting once I have something to show for it worth writing about

Edited August 2, 2016 by mickulty

[ObscureParadox_3XS]

That is the single most british reaction I have ever seen to a loud bang ever

[Guest TheMadDutchDude]

I just watched the vid, could have been a lot worse.

Like

 

 

smelting is refining ore and has nothing to do with melting metal of any sort as well.

 

I swear that is the exact replica of the first 3DMark 06 GPU test ... sparks flying and then the box getting shot off with the camera shake ...

 

Does anyone else see that?

[K404]

I want this guy at a bench meet

 

Also, on the subject of British reactions.....

[mickulty]

I melt all sorts of metals here, in fact I'm a blacksmith. Mild Steel crucibles work fine for aluminum if there think. I prefer graphite clay myself, but I have a big steel bowl I use for bigger pores. If your steel crucible is glowing bright red your too hot, dark red is more then ok. But if you get steel too hot the aluminum will mix with the oxide layer and eat the steel up, don't even think of using stainless, heat that up with aluminum in it and it's a goner.

 

Also alway, ALWAYS preheat you molds and crucibles.

I also casted my own heat sinks befor, just make sure you have away to keep the internal structure from being poorest, applying pressure to the metal wile in the mold helps. But cast heat sinks are never that good.

 

I use a hard wood forge with a hand crank blower to melt everything from aluminum to steel. yes I melted steel before, more so on accident when forge welding.

 

 

Edit:

If you need any pointers shoot me a pm. I'd be more than willing to help out.

 

I think it's a pretty fair assessment that we were running too hot in the past - too much impatience and an assumption that our improvised furnace couldn't get that hot. The steel crucibles were also thinner that would have been ideal as they were made from the bottoms of old (thoroughly flushed, ofc) gas cylinders, and resting on irregularly shaped coals so I'm guessing that won't have helped. Didn't think of the aluminium messing with the steel though, makes sense I guess.

 

Our mk1 crucible was a really silly one, a tiny argon gas cylinder cut in half and we tried to use both halves as crucibles. One of the crucibles had a brass valve in the end of it. D'oh! Besides, they were annoyingly small.

 

Also, hope it's ok for me to ask a couple of questions here - I tend to prefer asking publicly for the benefit of any lurkers/googlers who may come across it.

 

• How would you preheat the mould - blowtorch?
  
• We were thinking of using a mixture of around 80% sharp sand and 20% fireclay for the moulds - where does that sit on a scale from 'about right' to 'terrible idea'?
  
• How would you apply pressure - flat clay-lined lid or sheet of steel with a couple of bricks on top or something?
  
• My plan for the contact surface was to make the pattern a bit too big in that direction then sand it down to get a perfectly flat surface, sound good?
  

 

I really appreciate the pointers you've already given me, we had been putting the crucible in when the furnace was already hot which is probably a bad idea and hadn't even thought of preheating the mould.

 

I just watched the vid, could have been a lot worse.

Like this

 

Wow. Yep, that would have been worse. TBH we were lucky no molten metal was involved.

 

smelting is refining ore and has nothing to do with melting metal of any sort as well.

 

I appreciate the correction, I'll stick with 'melting down'.