Aluminum Scuba Tank for Forge?

T

Theforerunner

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Jul 11, 2018
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I was skating around town with my lady last summer and I spotted a blue tank on the side of the road and I immediately thought it would be good for a forge. It wasnt until i got it home that i realized that it was a scuba tank and made out of aluminum. Ive been reading a few different posts that suggest using aluminum tanks to make forges out of and it seems like, (upon Stacy's advice) that if its insulated well enough that it should work just fine.

Until now ive been using a square forge made out of fire bricks held together using angle iron and a migtipped venturi burner. Ive been considering using a 20lb propane tank to make a properly insulated forge but if i could use this tank I think it could be better no? I Just picked up a 120 lb anvil and an really excited to get into actual forging after having spent the last couple years doing stock removal exclusively. I can forsee trouble and heartache in my future if i dont at first set myself up with a really nice and hot forge. I think i would definitely like to buy once and cry once with something like this since ive rencently just built a brand new 2x72.

It sounds like with whichever way I decide to go, some sort of liner would be paramount in addition to the k wool insulation eh? I was going to build a new forge a couple years back until i came across a post talking about silica inhalation from refractory materials and something about ancient Rome etc etc lol.... scared me off a little about using a forge that has kwool in it... so some first hand knowledge or tips about safety with these sorts of materials would be much appreciated.

Id love to be able to get stuff hot enough to forge weld, with plans to make a billet press out of a log splitter.

thanks.
 
I'm no expert but that doesn't seem to be a good idea since the melting point of aluminum is apparently 660 degrees C (or 1220 degrees F).

See: The Melting Point of Metals

And as I recall from Larrin's articles the forging temp of most blade steels is around 1200-1300 degrees F, which would put that around the melting temp of aluminum.
 
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One would think it to not make much sense but I’ve never measured the external surfaces of my forge to ever be over 200 degrees F and I’m sure with wool and a liner and all it would probably do better. I’ve seen a post where Stacy has also mentioned the same. I guess where I start to see an issue would be the ends. Assumedly the tank would need to be chopped off at both ends and doors would need to be made out of steel.
 
If the forge gets to the melting point of aluminum, something is drastically wrong with the construction.
The refractory and insulation used in making a forge will protect the shell from most of the heat generated inside. I never shot a temp reading on the outside of the forge but would guess it is less than 400°F at the hottest place near the ports. I can put my hand on much of the forge.

You can make a forge shell out of most any reasonably rigid and reasonably heat resistant material. Aluminum will work fine for the shell. Use firebricks and/or steel in any areas exposed to the flames (like the ends and work shelf). Heck, it doesn't even have to be a round tube, square or rectangle work just fine for most forge builds.

With so many possible forge shell possibilities, the scuba tank would probably be best used as a quench tank.

Forge shell ideas - the world is littered with tings that can make a forge shell or quench tank:
Any straight sided can - potato chip can, trash can, lard can, metal 5-gallon paint/oil/grease/etc. bucket, etc. It does not need to be thick or heavy. It will work even if it is somewhat tapered.
Any type of metal pipe/tube - iron, steel, stainless ... if it is round it will work.
Sheet metal - roll up a piece of sheet metal and screw or rivet it into a tube.
Hardware cloth or rabbit wire - The heavy screen material can be sued. Roll it into a tube and fill it with the insulation. Don't worry if it is galvanized, it won't get hot enough to melt.
Old soda tanks, Old fire extinguishers, Old compressed gas tanks, Old propane tanks, helium tanks, air tanks, surplus ammo and mortar cans ......

A visit to a dump, junk yard, or scrap yard will turn up many future forge and quench tank objects.
Keep you eyes open for industrial and manufacturing places that have stuff laying around. A polite introduction and request will almost always get a free item.

You can be creative, too. The outside is just a surface and has no function in the actual use. - One fellow made his look like a jet engine, another a rocket engine, and one was made from an old bomb casing.
Now, if you want to make your forge really unique, steampunk it up with valves, coils of copper tubing, faux steam whistles, and any cool or unusual object you find in your junk box.
 
2” of insawool and 1/4” of satanite and the aluminum shell would be fine. Now you would be left with a pretty darn small chamber.

A quench tank would be a better use of the scuba tank.
An empty Freon of helium tank would be a more appropriate size a propane tank is usable but a bit large for most needs.
 
I used a 30 lb propane tank picked up at propane place - they usually have several "not usable" tanks around for free.
 
Same with "out of date" or "test fail" large size compressed gas tanks. The welding shops and gas suppliers have them sitting out back. Most will charge you around $10. If you tell them what you are going to build with it it may end up free. A 240 will make a nice forge and a quench tank.
Same for propane tanks from 20 to 60 pound size. They will often take off the valve and give you the old tank for free.
 
I have a different perspective.

If the scuba tanks is usable and sellable as a scuba tank, sell it and use the cash for your build.



I've never had a gas supplier sell a bad cylinder.
Either they revalve, retest and refill, or they destroy it.

Old soda pressurized tanks are in demand by the home brew crowd for making at home draft beer.
Pick them up free if you can, but craigslist them for the cash and get supplies.


Propane tanks, there are also companies that revalve, retest, repaint and resell.
However they are cheaper and it's easy to pick up a few bbq tanks for free.
They are not refillable if you have visible rust, so folks often toss them.

Flip them upside down, put the valve in a bench vise, turn the tank with a chain wrench, or a couple of chain visegrips
Clean out the stinky stuff with a bit of bleach water rinse.
 
Maybe it's different in Canada.
I got four large cylinders from my gas supplier that failed the water test - a 320cf, and three around 240-270cf. They charged me $20 for the lot.
The main propane company has tanks sitting all around the had rust or other cosmetic damage and couldn't be filled. They pulled the valves and gave me a 40 and a 20 for free. Salvage yards around here have lots of good forge building candidates for only a bit above scrap metal price.

If the scuba tank was at the trash, it may be damaged and unsellable. I don't think you could sell it without having it certified. I have seen what happens when a scuba tank explodes ... it isn't a pretty sight. The one I saw killed two people and destroyed a van.
 
Due to the limited space I have in my workshop (literally a 12x12 shed with extra steps) I think im leaning towards the 20lb tank option with two burners. I know the last time what discouraged me from going for it was reading about silica inhalation, something about the Roman stone masons dying from it all the time etc etc lol. Sounds like the smart thing is to do a combination of wool and cement material.

Another thing that’s probably impeded progress is that my current setup is just a bunch of bricks lined up in an angle iron frame and comes apart in a few pieces, which makes it easy to tear down and put out of the way when it cools. I haven’t even tried to forge on my new anvil with it yet because I feel like I’ll be spending too much time reheating. Something makes me feel like if I have a bitching forge it will make the rest of the process feel easier and more fun… lol
 
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