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lynnl
11-04-2002, 05:25 PM
When I was just a lad (probably 5 or 6 yrs old) my dad once showed me some magic with some metal filings, from an ax that he was sharpening. He ignited them and produced an impressive flash of fire with lots of pretty sparkle. Don't remember much of a noise other than a 'pooofhf'. Over the years I've tried to recreate that whenever I generated any fine metallic powder, but never with any success. I've since learned of the thermite welding process which, if memory serves me, uses aluminum oxide. He was an aluminum worker with Reynolds Aluminum, so he may have combined some other component, but I'm sure the filings from the steel ax was part of his concoction. Can anyone shed any light on this? I've pondered it for the last 50 years, and never thought to ask him while he was still living.

Rotate
11-04-2002, 06:47 PM
Did he use oxygen? Metal filing or even steel wool will burn very rapidly and brilliantly when oxygen is available in high concentration.

Albert

David Hafnorske
11-04-2002, 08:16 PM
Funny you should mention that he worked with aluminum. As I was reading your post I was thinking to myself that you could do this with magnesium (they use it to make aluminum harder) but I don't know how you would do it with steel. Magnesium is a flamable metal. Maybe he mixed some with steel filings.

Dave Burnett
11-04-2002, 08:54 PM
Probably added a little black with some aluminum dust.

gvasale
11-04-2002, 08:56 PM
you can toss powdered milk into a open flame. Poof! great at Boy Scout campfires.

Dave Burnett
11-04-2002, 08:57 PM
Sorry I left out a word. Black Power and aluminum dust.

WJHartson
11-04-2002, 11:28 PM
lynnl,

I can't tell you what he used but I can say it wasn't aluminum oxide AL203. It is used as a fire retardent among other things. I also worked in the aluminum industry for Kaiser.

He could have used Magnisum or metalic sodium. Both are used in the aluminum industry. The sodium is very dangerous and must be stored in oil to stop it from self igniting. Once the sodium picks up water it ignites.

The thermite process uses steel and aluminum in the presence of oxygen. Once the steel and aluminum are molten in an oxygen rich environment the process will continue as long as there is fuel and oxygen. It will cut through anything in the lancing process. The welding process is done with the same things in a confined space. Railroad track, large shafts etc. can be welded with this process.

docsteve66
11-04-2002, 11:34 PM
I was at a propeller polishing place once. A man there took a hand full of the dust and it burned with a match. I havenever been able to replicate that either.

I think your father was showing some "home made " Thermit (spelling is corrct). According to "AUDELS Welders Guide" 1967, Thremit is roughly three to one mixture of aluminum and iron oxide. (from my memory- there are several iron oxides). Audel says the iron oxide used is magnetic. The reaction is not explosive but fast. We played with some commercial thermit once. it seemed safe but it was in a mold.

According to audel, the reaction temperatures are computed to be 4559 degrees usualy rounded to 5000 degrees. (f).

First thremit weld I ever saw was at U S Gypsum, Greenville mississippi. A roughly 18" hydraulic shaft was welded with wax mold and clay. The result looked almost machined but was a large lump around the shaft. Took days for it to cool and havethe mold broken off. very pretty thing to see.

I suspect it is hard to keep the aluminum from becoming aluminum oxide. Chemicaly, the reaction is : 8Al+3 Fe3O4 yields 9Fe + 4Al2O3. When melted the iron floatsthe Al compund to the top leaving pure iron below. The manufactured mixtures have other alloying materials included with the iron.

I have told you considerably more than I actualy know about the process so proceed with caution if you use any of this info- including betting for beers.
Steve
PS: like Trhud, I love fire works of any kind

docsteve66
11-04-2002, 11:38 PM
Apparently external oxygen is not required. Audel as Mr Hartson says, has picutres of thermite welds on rail road rail and locomotive frames.

WJHartson
11-05-2002, 12:15 AM
The oxygen (part of the heat source)is needed to get the process started for welding. Once it start it will continue in a closed environment. In lancing the oxygen is part of the process. Usually Oxygen and acet are used throughout the process to keep it going. The acet has to be manifolded so that 1/7 of the contents of the cylinders are not emptied per hour or you will start pulling out the acetone. If you can keep the heat up the acet can be reduced of completely shut off.

Treven Baker
11-05-2002, 01:26 AM
I;ve seen themit melt some thick steel realy fast! In october we have the California Black Smithing Octoberfest and the guy who hosts it has a bunch of themit. Late saturday evening he gets it out for a show. There is alot of fun stuff he does with his 500 ton hydrolic press as well. If you want to see metel move go to this event!

SGW
11-05-2002, 07:44 AM
There's the famous (or infamous) MIT hack pulled by some students, years ago. For those who don't know, Cambridge, MA, has electric streetcars that run on tracks. When the car stopped to pick up and let off passengers, a group of students kept the driver busy making change, etc. to keep the car from moving. Meanwhile, another group of students set off some thermite between a car wheel and the rail...and welded the car wheel to the track!

At least, that's how I heard it....

I should point out that, strictly speaking, this wasn't a true "hack" because it caused actual damage. A true MIT hack should not cause damage, just be clever.


[This message has been edited by SGW (edited 11-05-2002).]

hms50
11-05-2002, 10:51 AM
In the old days, magicians used to use lycopodium powder to make a brilliant flash. It turns out the powder is the dust- like spore from inside a puff ball. The trick is to suspend the powder in the air so lots of o2 is mixed with it. Pure aluminum will do this if you toss it in the air and hold a candle or match to it. Aluminum is the magic substance in flash powder. That's whats inside big scary firecrackers. By the way, flashpowder is very dangerous stuff. It can detonate all by itself under some situations and is also sensitive to friction or shock. Nothing to have laying around!
hms50

FLPR@juno.com
11-05-2002, 11:34 AM
A typical way of starting the thermit reaction was to place a small amount of magnesium powder on top of the thermit mixture and ignite the magnesium.

George Hodge
11-05-2002, 10:15 PM
Next time you machine some iron castings,take some of the fileings and toss it in a fire. about the same thing as Fourth Of July sparklers.