Titanium - hdbk10810036

PYROPHORIC METALS

DOE-HDBK-1081-94

Spontaneous Heating and Pyrophoricity

methods which depend on water, water solutions, or inert gas are not effective on

magnesium chip fires. Halogen containing extinguishing agents (the Halons) react

violently with burning magnesium because the chlorine or other halogen combines

with the magnesium. However, flooding with noble gases (e.g., helium or argon)

will extinguish burning magnesium.

The method of extinguishing magnesium fires depends largely upon the form of the

material. Burning chips, shavings, and small parts must be smothered and cooled

with a suitable dry extinguishing agent (e.g., graphite and dry sodium chloride).

Where magnesium dust is present, care must be taken to prevent a dust cloud from

forming in the air during application of the agent because this may result in a dust

explosion.

Fires in massive magnesium can be fought without difficulty if attacked in their early

stages. It may be possible to remove surrounding material, leaving the small quantity

of magnesium to burn itself out harmlessly. Considering the importance of prompt

attack on magnesium fires, automatic sprinklers are desirable because they provide

automatic notification and control of fire. While the water from the sprinklers may

have the immediate effect of intensifying magnesium combustion, it will serve to

protect the structure and prevent ignition of surrounding combustible material. An

excess of water applied to fires in solid magnesium (avoiding puddles of molten

metal) cools the metal below the ignition temperature after some initial

intensification, and the fire goes out rapidly. By contrast, the fire may be intensified

but not controlled with only a small, finely divided water spray.

Magnesium fires in heat treating ovens can best be controlled with powders and

gases developed for use on such fires. By using melting fluxes to exclude air from

the burning metal, fires in heat treating furnaces have been successfully extinguished.

Boron trifluoride gas is an effective extinguishing agent for small fires in heat

treating furnaces. Cylinders of boron trifluoride can be permanently connected to the

oven or mounted on a suitable cart for use as portable equipment. Boron trifluoride

is allowed to flow into the oven until the fire is extinguished, or, where large

quantities of magnesium are well involved before discovery or where the furnace is

not tight, the boron trifluoride will control the fire until flux can be applied to

extinguish the fire.

Titanium

Properties

Titanium, like magnesium, is classified as a combustible metal, but again the size and

shape of the metal determine to a great extent whether or not it will ignite. Castings

and other massive pieces of titanium are not combustible under ordinary conditions.

Small chips, fine turnings, and dust ignite readily and, once ignited, burn with the

Pyrophoricity

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