I have a request from a client to cut some titanium sheet with a plasma
torch. The torch I have uses air and I'm a little concerned by the MSDS
on titanium where it says that the dust is quite flammable and the the
metal will ignite in air at 1200 degrees centrigrade. Anybody have any
experiance doing this sort of thing? Any comments on the safety issues?
What is the likelihood that I will set the sheet of titanium on fire
with the torch.
--Been there, done that; never had a problem with a spontaneous
fire, but the process does generate gobs of smoke, so do it in a well
ventilated area. Leaves a gawdawful burr on the backside and you'll have to
grind that off, too.
Steve Schlaifer fired this volley in
The likelihood is rather large, and titanium burns readily in atmospheric
oxygen, once ignited.
You need inert gas for this, and it wouldn't hurt to do the cutting in a
"tent" flooded with gas above and below the cutting area.
Yes, don't do it. Would you cut magnesium with a plasma? Ti is
nearly as flammable, once you get it hot. The dust would be
oxidized, and not too bad, but once the side of the cut gets hot
enough, WATCH OUT! This might only take seconds after the punch
through before the whole plate lit off. Once ignited, it would
be extremely hard to put out, with white-hot tracers flying
around. Putting water on it will cause a huge "explosion" of
molten metal, the only thing that is likely to work is embedding
the whole mess in sand dampened with fire retardant foam.
If you have any doubts about the specific alloy, ask for a SMALL
piece and try it over a bucket of sand. If it explodes, you
have your answer. If it doesn't, that doesn't prove it is safe,
just that that particular alloy less flammable.
And, maybe I'm off base, I just know that you need extreme
precaustions when doing any welding on Ti. Generally you use
extra shielding gas on the back side of the weld, and accidents
The pigment generally used for white in paint is TiO2, which would be
the product generated during the cut. I bet the smoke was white, and
depending on particle size, very thick. Hopefully, the thermal
conductivity of titanium would be high enough to cool the haz below
the temperature needed for combustion under most conditions, but who
knows? Sounds nasty.
I might also be way off base here, but I think that the reason for
all the precautions with Ti is to ensure a good quality weld, not to
specifically prevent a fire. Ti oxidizes readily, and the oxides aren't
very strong, hence the need for a well shielded welding zone. I've never
heard of any metal fires starting in the bulk material, only in the
swarf. Keep in mind that one of the attractive features of titanium is
it's high heat strength, hence it's use inside of jet turbines, a
horrendously hot environment. Of course YMMV. This is probably a good
question to ask over in sci.engr.joining.welding.
and look at the 'recommended processes' near the bottom. Ti and Mg are
listed as ok.
Also check out lots of
good info there.
One thing to be careful of, not just in the case of Ti, is mixing of
swarf of different metals, which can cause a a much bigger reaction than
that of a single metal. (think thermite)
You can cut Ti just fine with a plasma cutter.
It does produce an amazing amount of white light.
Can be rather startling the first time.
You will have a burr on the metal after the cut, and a heavily oxidized
edge that would need to be ground before any welding.