So that you will have a deeper insight into the mechanics of track, the elements making
up track are discussed in detail in the paragraphs following. To have more than the trackwalker's
appreciation for defective track, a person must understand the capabilities and design of the track
components.
3.3.
RAILS OF STEEL
The greatest difference between Stevens' and today's rails is not immediately noticeable
because the difference is in their composition. Stevens' rail was rolled iron while modern rail is
made of steel. Stevens knew that steel possessed qualities that made it superior to iron for rails,
but the method of its manufacture at that time made its cost prohibitive for any uses but those
requiring only small quantities. His selection of rolled iron for rails was appropriate and
justified. Later, when the Bessemer process for making steel was developed, steel rails became
practical. The greater resistance of steel to impact, its higher ultimate strength, and its greater
resistance to wear were exploited when steel could be made in large quantities at a reasonable
price.
The Pennsylvania Railroad, now the Penn Central, was the first company to use steel rail
in the United States. This rail, like the first iron T-rail, was imported from England in 1863. The
first American steel rail was produced in 1865.
3.4.
METHOD OF MANUFACTURE
The Bessemer process for making steel was used for many years. Today the open-hearth
process is much more common. In this process, pig iron and scrap steel are melted in a furnace.
Air is blown across the molten metal combining with and removing carbon, a lower content of
which being the major difference between iron and steel. The carbon content is brought below
the desired level; then the metal is recarbonized to the exact requirement. Other alloying
elements, such as manganese, are added. The furnace or hearth is then tapped and the molten
steel poured into a ladle. Each batch so prepared is known as a heat of steel and is given a heat
number.
The molten steel is poured into molds and cooled. When the steel has solidified, the
mold is removed, leaving an ingot. The ingots receive heat treatment and then are rolled into
blooms about 8 inches square. The bloom is an intermediate stage in form between ingot and
rail. At the rolling mills, the bloom becomes a rail. All this rolling from ingot to rail is done
with the steel at high
40
Previous Page
