true circle. The wheels are then branded with the appropriate symbols and allowed to cool under properly
controlled conditions to prevent weak spots from forming in the steel.
The manufacturing process of multiple-wear, wrought-steel wheels includes an additional heat treatment
of either the wheel rim or the entire wheel. This treatment increases the hardness of the metal and causes the
wheel to wear longer before reaching the wear limits. The letters R for "rim treated" and E for "entire wheel
treated" are stamped on the wheel along with other information.
2.6. WHEEL MARKINGS
Both cast-steel and wrought-steel wheels bear markings that provide a skilled observer with complete
information about the wheel. The markings, although giving generally the same information, are displayed
differently on each type of wheel.
a. Cast-steel wheel markings are hot stamped on the back face of the rim or cast on the back plate of the
wheel according to specifications given in the AAR Manual of Standards and Recommended Practices. Figure
2.1 shows the markings on the back plate of a wheel. In letters at least 1 inch high, the marks show the month,
Figure 2.1. Markings on Cast-Steel Wheel.