How It's Made - Alloy Wheels

Discovery and Science Channel's How It's Made Alloy Wheels episode.

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Closed Caption:

higher end cars typically come with
alloy wheels rather than basic steel
wheels covered with a hubcap called mag
wheels because when they first came out
they were made of an alloy of magnesium
today's alloy wheels are made of an
aluminum alloy which is far more durable
aluminum alloy wheels are not only more
attractive than standard steel wheels
they're also a fraction of the weight
and therefore require less energy to
rotate this contributes to greater fuel
efficiency as well as better handling
acceleration and braking manufacturing
them begins with high-grade aluminum
alloy containing ninety-seven percent
aluminum a furnace heats the ingots -
750 degrees Celsius
they liquefy in about 25 minutes
the molten aluminum then flows directly
to a mixer in which they inject argon
gas which enables them to remove the
hydrogen
this increases the density making the
aluminum less porous when solidified
after adding powdered titanium magnesium
and other metallic elements to further
strengthen the aluminum they blend in
flux at chemical which draws aluminum
oxide to the surface they skim off this
impurity along with the flux and the
liquid aluminum is ready for casting the
wheel mold is made of high-strength
steel
it's actually a set of three molds the
upper mold which forms the inside face
of the wheel
the four parts I'd mold which forms the
wheels edge and the lower mold which
forms the outer face
that's the side with the design so this
is the most intricate mold
it takes three to four weeks to produce
some old computer simulations check the
flow and temperature of the liquid
aluminum factors critical for preventing
casting defects the casting machine is
designed to fill the mold from the
bottom by pressurized injection
injecting upward through the bottom
rather than pouring downward into the
top reduces the risk of air bubbles
which cause defects right before casting
the molten metal flows through a filter
sheet made of high temperature resistant
ceramic this traps additional aluminum
oxide once cast the aluminum takes about
seven to ten minutes to solidify then
the mold automatically opens releasing
the newly cast wheel workers submerge it
in lukewarm water for a few minutes
this cools it down enough to be handled
the wheel undergoes a complex heat
treatment process that takes 12 hours
from start to finish first
they heat the wheel to 500 degrees
Celsius this rearranges the molecular
structure strengthening the metal next
what's known as quenching they submerge
the wheel in 80 degree water for 30
seconds
this locks in that new strength then
they reheat the wheel this time to 180
degrees for nine hours to further
stabilize the metal the wheel doesn't
come out of the mold in perfect
condition
the edges are rough due to some excess
metal that has to be trimmed off so they
mount the wheel on a computer-guided
lathe it precision machines the sides
refining them to within point zero five
millimeters of the measurements
specified in the technical drawings as
for the more intricate face of the wheel
a worker manually trims the edges with a
blade
the shape now finalized
it's time to test the wheel to make sure
it's airtight
while pumping air into the wheel
they submerge it in water should any air
bubbles appear
it would mean there's a pin hole in the
metal or some shrinkage in which case
the wheel would fail inspection
no air bubbles the wheel proceeds to the
automated painting line first a base
coat then a coat of color which can be
anything from classic silver or black to
a flashy or shade then a clear coat to
protect the paint and prevent corrosion
from every fifteen hundred or so wheels
the factory randomly selects two or
three to test for performance and where
workers install the decorative cap that
covers the center hub
it typically bears the specific brands
low go then the final cosmetic
inspection to make sure these aluminum
alloy wheels look as good as they
perform