ADVANCED
TECHNOLOGY
Griffin's
unique process: pressure pouring in a graphite mold
Controlled pressure pouring, a patented process developed
by Griffin, is used in all four of our North American wheel
plants.
 How it
works
A ladle of molten steel is placed in
a chamber and sealed with an airtight cover. A ceramic tube is attached to
the cover. Air forced into the chamber pushes the steel up through the tube
and into a graphite mold positioned over the pouring tube. The steel fills
the mold from the bottom to form the wheel.
Close
tolerances
Because the
steel is forced into the mold at a controlled rate,
the wheel is cast to extremely close tolerances.This
produces a wheel to such close tolerances that
it eliminates the machining required in other railroad
wheel manufacturing processes.
Close
control over chemistry
Electric-arc
furnaces at all Griffin plants give precise control
of the chemical properties of the steel. Spectrometers
closely monitor steel chemistry for the best
metallurgical characteristics needed for tough
service and long life. The flange and rim of
a Griffln wheel are exceptionally durable. The
carbon content of the steel meets AAR M107/208
Quality control and beyond
More freight cars ride on Griffin steel wheels than on any other brand. And
our wheels have logged billions of service miles. Beyond the patented controlled
pressure pouring process, there are many more good reasons for this record
of success.
 Controlled
heat treatment
Every Griffin wheel is normalized in a gas-fired rotary hearth furnace. This
improves metallurgical structure and relieves internal stresses. The wheel's
rim and tread are also rapidly cooled using a water spray to increase hardness.
Magnetic particle testing
Griffin was the first manufacturer to use 100% magnetic particle inspection
for surface flaws. Magnetic particle inspection stations check each and every
wheel. This procedure was later adopted by the AAR as a requirement for all
wheel manufacturing processes.
Ultrasonic inspection
Griffin was also the first manufacturer to ultrasonically inspect 100% of its
wheels prior to shipment. All ultrasound transducers are fully automated
and computer controlled for maximum test reliability. Again, the AAR has
adopted this procedure as a standard.
Better weight-to-strength ratio
Griffin's parabolic/deep dish wheels attain a better ratio between minimum
weight and maximum strength. |