Furnaces
are quite remarkable devices. Since prehistoric times,
naked men have been building furnaces for melting all
sorts of metal and metallic alloys. Through the ages,
the design of the traditional coal/charcoal powered
furnace has evolved only very slightly. This is the
design to be built here in Penguin's Lab (but please,
skip the naked part).
Of
course, there are other more efficient, and perhaps
more high tech furnace designs out there which utilize
propane, oil, or even electricity. However, I decided
to give the charcoal furnace a shot, given its remarkably
simple design and effectiveness. |
Pouring
molten aluminium into ingots (details below) |
Melting
an aluminium heatsink in a regular fireplace |
At
first, I did not believe that aluminium was an easy
metal to melt. So I devised a very simple strategy to
see whether or not there was still any hope of smelting
aluminium...
The
(ultra crude) strategy
was to dump an aluminium heatsink in a ceramic cup and
leave it in a fireplace overnight on top of hot coals.
I
must here acknowledge the assistance I have received
from several people during this project. Daniel Huang
has been extremely generous in allowing me access to
his fireplace and bearing the risk of having molten
metal in the room. Ben Myers has been a great help in
scavenging materials around uni at night, and I can
say he has a great eye for spotting aluminium. |
The
next day, I peered into the ceramic cup only to find
slag deposits.
Upon closer inspection, the cup had actually shattered
into hundreds of pieces and I managed to find this lump
of aluminium beneath the fireplace grate.
I
could not believe my eyes! I may exaggerate, but it
was a feeling similar to what you'd experience if your
portfolio at Fisher
Investments had tripled in value in just a day.
I was confounded, to say the least. The heatsink had
completely melted and dripped through the grate, forming
this ... very "interesting" looking shape.
This lump is what ignited my passion for smelting metals.
I could not wait to start casting some more aluminium
(albeit perhaps in a more aesthetically pleasing shape). |
This random
lump of aluminium was found underneath the fireplace
grate
|
At work with
the dodgy furnace
|
I knew the fireplace would do the trick, but I thought
perhaps if a steel can was to trap most of the heat
in...?
As
you can see, this lead to the creation of a "Milo"
furnace (if you can even call it a furnace) made from
a Milo can and a tuyere hole at the bottom for pumping
oxygen in. Of course, in all my eagerness to get started,
I did not give a damn about what a real furnace needed:
Refractory?
Nah no way, can't be bothered.
Blower?
Umm... I'll use a hand pump.
Lid?
I suppose the Milo can lid will do.
Crucible?
Too lazy to find one. I'll use a smaller Milo can.
I
call this the dodgy furnace... |
Having
almost no idea what I was doing, I loaded the base of
the dodgy furnace with a bunch of charcoal bits and
some scrap wood as kindling. With the help of the hand
pump, I was able to get some pretty flames. The improvised
crucible was loaded with scrap aluminium and dumped
in. I then pumped away and hoped for the best... |
The dodgy
furnace spurting out a nice flame
|
The first
ingot!
|
After
about half an hour of pumping, the sides of the dodgy
furnace were glowing red hot. So I decided to check
on the aluminium. It seemed liquid enough, so it was
poured onto this brick which I use as an ingot. |
Here
is the result of the first and final pour from the
dodgy furnace. The brick has its brand engraved..
"Nubrik". However, there evidently wasn't
enough aluminium to produce a full ingot. But I was
quite amazed that such a dodgy furnace could melt
anything...
The
dodgy furnace was decomissioned after its first use
because, upon later inspection, both the crucible
and the furnace itself had massive holes in them from
some serious oxidisation during the melt.
|
The yield
from the dodgy furnace
|
Scrap
aluminium ready to be pulverised then melted |
After
the spectacular failure of the dodgy furnace, I was
now prepared to take a step back and design a proper
one. However, having no materials on hand at the time
meant that this was only feasible after returning
home to the lab - a few months away.
In
the meantime, I decided to muck around with the direct
fireplace melting method again. Here is some scrap
aluminium picked up from uni that will be melted in
the next fireplace run.
|
I
decided to stick to using a soup can as a crucible,
mainly because there were plenty around and I wasn't
expecting them to last more than one melt anyway.
Here
the crucible is loaded with the aluminium scraps mentioned
previously, dumped into the middle of some pretty
hot coals, and left to suffer.
|
The scrap
aluminium is heated in the fireplace
|
|
After about 20
minutes, the whole load is molten. Using a spoon attached
on a long stick, the slag is skimmed off and the liquid
aluminium is poured into brick ingot moulds, where
they will solidify.
The tongs I am
using were $1 from a charity shop. It feels quite
durable and has a high temperature plastic handle.
Score!
|
Immediately
after pouring, the molten aluminium glows a cherry red
and is extremely reflective. The surface becomes dull
after a few minutes into cooling, and small crystals
form shortly after.
I
have to say, this pour was much more satisfying than
the first! |
The ingots
are left to cool for half an hour before removal
|
Ingots
|
The result from
subsequent melts - not bad. The ingots contain a lot
of detail and are very smooth to the touch.
Some of the brick
is chipping away due to the intense heat from the
molten metal, but that doesn't matter. After all,
these are only ingots.
|
Some
further scavenging around the uni found some VERY nice
scrap aluminium. These hollow bars were previously used
to protect electrical cables from damage. A hacksaw
turned the bars into usable chunks of metal. |
Some awesome
scrap aluminium
|
Pouring molten
aluminium into ingots
|
Here is another
melt using, once again, another soup can as a crucible
and the latest aluminium scrap.
This is actually
a still capture from a video that I have not yet uploaded.
I might upload this in the near future when I can
get it into a more usable format.
|
Here
are the results of most of my melts in the fireplace
- about 2kg worth of near pure aluminium. The two larger
ingots at the bottom of the heap are the only "full"
ingots - the ones that almost spilled over the side
of the brick mould. The smaller one at the very top
was the result of some excess aluminium in the crucible
that had to be poured.
These
ingots will travel back home with me to be remelted
in the new furnace that will be built (details below). |
A family of
ingots - how beautiful!
|
A poor, battered,
and decomissioned crucible
|
Just
a shot to illustrate the poor condition of a soup can
crucible after a single use. Prior to melting, I hammer
in two holes on either side with a nail to accomodate
for a crucible lifter (none other than a single bent
coat hanger), and also a pouring spout.
Here
you can see a hole in the side of the crucible with
a bit of aluminium slag lodged in place. I have found
some soup cans to be tougher than others. Of particular
note are the ribbed cans that hold beef stew - these
last about three melts. On the other hand, tuna cans
proved to be extra dodgy, the one that I used developed
a hole in it before the first pouring, leaking molten
aluminium everywhere. |
