The Wright Twin Cyclone had magnesium accessory drive housings (they
dropped the magnesium crankcase due to design time problems) -- when
the exhaust ring broke, they usually caught fire and burned the wing
off of a B29 in about 90 sec. No extinguisher at the time would stop
the fire....
My brother has had a couple of magnesium fires at work, he's a
toolmaker. Unknown material, pretty light, hard to machine, he's
beginning to think it's probably magnesium when the chips ignite. Just
brushed all the chips in a pile and pulled the chip pan off the lathe
and shoved it into the middle of the room so the part itself wouldn't
ignite.
Magnesium burns under water, under CO2, and unless you can prevent air
mixing in, in inert gases as well. The heat of hydration is high
enough to keep it going, making MgOH instead of MgO, and the heat of
formation of the carbonate is almost as high as that of making the
hydroxide.
Titanium is similar -- once you get it burning your only choices are to
let it go, smother in sand, or blanket with an inert gas (argon or
helium) with no O2 or CO2 until cools.
Peter
