Thursday, March 24, 2016

Sand Casting with Aluminum

Ok, now this little project is getting real ;-)

We started with the aluminum ingots we'd made a few days ago.  They heated up quickly with much less junk.  We used the same crucible, so most of the junk in the metal was left from our heating the cans and brass cases.  The best part?  Cutting out foam forms!  We picked up a big sheet of foam from the Dollar Store, and with an inexpensive cutter off ebay (foam cutter $2) it was so easy to cut out some arrowhead shapes.  Even some 3D shapes were easy with glue.

We even tried a few 'exotic' arrowheads, including some 3D Fire Cage Arrowheads.

We buried the foam in play sand in a small tupperware bin.

Then we wett'ed the sand, and formed small cones around the foam to pour the aluminum into.  Here are some of the ingots we made last week to melt for the casts.

The ingots heated up quickly, and it was really cool to pour.  Again, because of the thin metal crucible we only got a single pour before the metal cooled too much and wouldn't pour well.

The casts turned out AWESOME!  Identical to the foam cutouts, and small details are in-tact.  We shook the sand well to make sure it settled into each detail.

These are a couple of "bird tip" arrowheads that Mongol archers would use for ducks and geese.

It was easy to cut off the overpour with a grinder and shape / sharpen the arrowheads.

We dropped paper on the overcast to show the kids just how hot the metal was before we pulled them and put them into water.

Unfortunately, the bigger, 3D casts of the Fire Arrowheads didn't turn out.  The metal seemed to have cooled too much to get down into the bottom of the foam mold.

Still, this was so much fun, we all agreed this is worth the effort to melt down cans.  Easy, cheap, and very engaging.  Highly recommend it.  Now we are having fun thinking of all the fun things to make...

Making Metal (part 3) "Going for the Gold!"

Ok, with a working kiln of fire bricks, we thought we'd try something a bit more difficult than Aluminum and Lead.  We had a bunch of 22lr brass we'd picked up when out plinkin' in the woods, and thought it would be fun to melt down some brass ingots.

Aluminum melts at ~1200*F, and brass at ~1500*F so this is going to take a bit more heat.

The brush torch got plenty hot.  Nice thing is we can crank up the heat fast and easily with it.  You can see the brass in the pot.  The pot was hot!  Most of it was 22lr, with a few 45 and 9mm cases.

Before long (~10 min) the brass was a gooey mess in the opt.

Again we put in some Boric Acid (from Dollar Tree) to help separate the junk from the metal.  It burned green, and foamed up in the pot.

The ingot was cool!  One drawback with our propane bottle crucible is that the thin metal cooled really fast, and we had to pour quickly before the metal inside cooled too much to flow well.

Again, there was a lot of foamy junk in with the brass we had to skim off.  Some of this was from the aluminum, too because we were unable to clean out the pot completely before doing brass.  Next time we'll have different crucibles for the different metals.

There wasn't a lot of brass when it was all finished.  Then again, we only started with 2 big handfuls of 22lr brass, so the yield was ok.  And the price is right.  Sure looks perdy, too.  Wouldn't it be fun to scatter small pieces of this in a stream or mountain brook?  We could start another gold rush ;-)

Smelting down cans and brass is great fun, and very engaging with teenage boys.  The results are fun too... but now we are ready for making something out of this mess.  Stay tuned...

Makin' Metal (part 2) "Turning up the Heat!"

So this time we bought some fire bricks, and pulled out the weed-burning propane torch.  This was the way to go!  We need something a little more fixed and secure - the bricks were just stood up on end and were a bit shaky... but it got HOT.

Feeding the cans in was quick.  A brick on top really made a significant difference, too.

In minutes the kiln got very hot.  Our welding gloves warmed up fast.

Again, the ingots turned out nice.  If you zoom in you can see the crystaline structures on the surface of the ingot.  We used a bigger muffin tin for this pouring, too.

Again, melting down cans left a bunch of junk.  We did a lot to skim off the junk from the top before pouring the ingots.  Keeping a bucket of cold water handy was useful and our safety precaution.

Our next step will be to do something useful with the aluminum.  We are also going to find a better source for aluminum to melt - we melted down ~100 cans to get a few big ingots, so it takes alot of time and effort.  We did add Boric Acid to the metal, and it foamed up on the top and seemed to help pull the junk away from the aluminum... but we aren't sure if it also made more of the foamy junk metal or not.  We'll see.  This has been a lot of fun!

Meltin' Metals (part 1)

We collected a few aluminum cans, and after lots of FaceTubing, we thought we'd try melting them down into ingots.

First try was with coal in the forge, while we pounded out some metal.  We cut the top off an old, used up propane tank.  This method was pretty slow but didn't cost anything.  It took us ~30 min to melt a can or two and we lost interest.

Our next attempt was with a #10 can and some ceramic paper.  The paper was off ebay, and we paid ~$6 for 3 sheets.  it took 2 sheets to line the can.  This time we punched a hole in the side of the can for the hand-held propane torch.

This method was MUCH faster - we melted ~30 cans in about 30 minutes.  Cheap, and fast enough it kept our attention this time.

The flame was concentrated on the one side of the crucible.  the heat spread, but not more than half way around.

The cans melted pretty fast, but we were surprised how much garbage was in the metal.  About half of the metal was unusable - and we had to do a lot of skinning off the top.

The ingots we poured into a small muffin tin. They turned out really cool!  You can see some of the 'garbage' metal, too.  Not sure if this is poor-quality aluminum or from all the plastic, etc in the cans.

Great fun, fairly fast, and pretty cheap to do.  $6 for the ceramic paper, $1.50 for the propane, and $2 for the muffin tin.  Worth a try!