[TheForge] Re: Burning Metal

[Mike Spencer]

> I heard that one can burn metal, but I couldn't find much
> information on it so I have a few questions:
>
>    What happens (molecularly) when metal is burned?
>    What metals can this happen to?

You can get picky about the definition of "burn".  Maybe you have to
because it simplifies the answer.

If you say that "burn" means 

   combining with oxygen (once it's ignited) at ordinary atmospheric
   temp and pressure for form an oxide and

   doing it exothermically, i.e. so that enough heat is released to
   keep the process going on its own,

then magnesium is the real winner.  You can ignite Mg ribbon with a
propane flame and it will burn like a fuse.  Once, before I knew
anything about blacksmithing, I decided to use an oxy-acet torch to
melt out part of an "aluminum" VW transmission case to make a starter
mount so I could start VW engines on an engine stand.  Just got going
good and the damn case caught fire!  Sat there burning on its own and
filling the shop with a plume of fine magnesium oxide particles and
transmission oil fumes.  *I* didn't know the VW trans case was
magnesium!  (A CO2 extinguisher worked just fine.)

If you change the definition to allow higher temps, then steel will
burn. As long as you keep the steel real hot, it'll sit there and burn
very nicely.  You can do this in your very own forge with something
you've spent hours working on. :-)

} ...thermite (a compound of iron and aluminum).

Isn't thermite a mix of iron oxide and aluminum?  The oxygen in
the iron oxide switches horses to the aluminum and the result is
aluminum oxide, molten iron and enough heat to keep the process
going.  So you have to change the definition again to allow combining
with oxygen that's already bound to other non-oxygen atoms in order to
say that the aluminum is "burning".

- Mike

-- 
Michael Spencer                  Nova Scotia, Canada       .~. 
                                                           /V\ 
mspencer@tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^

--