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Did you know? some metals heat
up very quickly under a flame and can become a greater burn hazard. Others
are brittle and can not take impacts and some can give off toxic fumes.
These are things your should know for your own safety!
The
facts about metal components
We have provided this useful
information so you can select safer, impact resistant, and longer life
fire twirling equipment. Please feel free to print for your own records.
 Zinc.
Zinc coatings on mild steel
extend the corrosion life by 20 times. However coating melting point
is low at between 400-450degC and when burnt can generate Zinc Oxide
fume which is toxic and an irritant, which may lead
to zinc or metal fume fever. However "Metal fume fever" is
a short lasting, self limiting condition with symptoms similar to influenza,
and unlikely with normal use. The fuel will be giving off toxic fumes
anyway. Zinc has a higher thermal conductivity than plain steel, so
watch out for burns from smaller zinc coated items. These items are
generally very cheap. NB: not used in our products.
Cast
iron or iron ore.
Some swivel clips and connectors.
Is very cheap, heavy, hard and very brittle so can
break on impact. Do not use.
Copper.
Copper has a very high thermal
conductivity and will heat up very fast under a flame. Watch out for
burns!
Aluminium aka Aluminum.
Common used Alloy 6063. Melting
point is 660degC. When melting will create a respiratory irritant. Softer
metal . Aluminium has a higher thermal conductivity (4 x )than plain
steel. Never use aluminium ball chain as it heats up quickly because
of it small mass and breaks very easily. However it is suitable for
tube core poi heads and as tube for a twirling staff if the wall thickness
is sufficient.
Brass.
Safer than Zinc with a higher
melting point of 940degC (twice that of Zinc) but with similar thermal
conductivity to Zinc. When burnt under extreme flame can generate Zinc
Oxide fume which is toxic and an irritant, which may lead to zinc or
metal fume fever. However "Metal fume fever" is a short lasting,
self limiting condition with symptoms similar to influenza, and unlikely
with normal use. The fuel will be giving off toxic fumes anyway.
Mild steel.
The melting point of mild
steel is 1515 ° C. This will rust with time unless
plated or coated. Coatings will wear off with time. Hardened carbon
steel is much harder than mild steel, but still brittle and with internal
stresses. Case hardened carbon steel provides a tough interior while
providing a hard, but more brittle exterior. With many months of heating
and cooling we have seen high impact components snap so be careful where
this metal is used.
  Dangerous
use of Mild steel key/split rings: Continuous heating
and reheating of these rings with any centrifugal forces causes the
ring to open up. Standard cheap low carbon key rings will weaken
at 260 Deg C. within 2 minutes!
Even small stainless steel
splitrings will open. Remove risk, increase product safety and product
life by using stainless steel quicklinks. See Stainless
steel quicklinks and parts
Nickel Plated Steel.
Nickel is tougher than iron and is harder and more durable.
Nickel provides greater abrasion and corrosion resistance.
Overheating will cause nickel plating to come off mild steel. However
it will not melt under 1450degC. when it would then become an irritant
of the eyes, nose and throat.
 Type
304 Stainless steel.
Type 304 stainless
steel contains iron, nickel and chromium. It is this addition of
chromium and nickel that gives the steel its unique stainless,abrasion
and corrosion resisting properties. Although not as hard as
high carbon steel it provides high strength without brittleness.
With a melting point of 1420degC, after which it will then irritate
the eyes nose and throat. Stainless steel has a much lower (1/3)
thermal conductivity than plain steel and will heat up under
a flame much more slowly so the effect of any burns will be less.
Benefits of stainless steel include: Corrosion resistance,
Fire and heat resistance (retains strength), attractive
appearance, strength to weight advantage, high impact resistance, and
very long life.
With so many benefits stainless steel is the preferred alloy for use
on fire twirling equipment.
See also Your
guide to ball chain cords and components , Stainless
steel equipment and parts, Fire
poi
References: HSE
UK, Nickel institute, Fire
Science and Technology, The
stainless steel information center, American
Iron and Steel institute, Fire
research information Services
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