are put into a furnace for tempering to meet required hardness and then cooled under controlled conditions.
One-wear, cast-steel wheels are still in service but their manufacture has been discontinued.
2.5. WROUGHT-STEEL WHEEL
New two-wear and multiple-wear wrought-steel wheels are generally used on passenger cars, and on high-
capacity engines and freight cars. The one-wear wheel is lighter in weight than the multiple-wear wheel and is
designed for use primarily on freight cars. Multiple-wear wheels are used initially on passenger cars, and when
they are worn to condemning wear limits, they are turned down and restored to original contour and used in
freight service. Manufacture of the two-wear wrought-steel wheel has been discontinued. Those still in service
are marked AAR-2-W.
The same five classes of cast-steel wheels (par. 2.4) apply also to wrought-steel. One-wear wheels,
designated AAR-1-W, have a minimum rim thickness of 1 1/4 inches; multiple-wear, marked AAR-MW, are of
heavier construction with a minimum rim thickness of 2 1/2 inches.
The fundamental principles used by manufacturers to make wrought-steel wheels are similar, but they
differ in detail. These wheels are made from ingots produced by the open-hearth process of steel manufacture.
The open-hearth furnaces usually have a capacity of from 60 to 100 tons; they require from 8 to 12 hours to
produce steel ready for pouring from iron and steel scrap. Within these furnaces the molten metal is boiled
thoroughly to destroy the impurities and to expel the injurious portions to obtain a homogenous steel containing
from 0.7 to 0.8 percent carbon.
Once the molten metal is ready for pouring, one of three methods is used to produce a block or ingot of
steel of suitable weight to shape a wheel: (1) a cylindrical block is produced by rolling a large ingot to a wheel
bloom 15 to 18 inches in diameter and then hot-shearing (cutting while hot) it to a suitable length; (2) an ingot is
cast and then cut when cold to the proper length; or (3) a block of suitable weight is cast in the form of an
individual ingot. After the ingots are poured and sized, they are called wheel blanks; these are then rolled into
wheels while being rotated on either a vertical or a horizontal plane. The wheels, after the rolling process, have
straight plates which are coned or dished by a final pressing operation. At the same time, the circumference of
the rim is formed to a