Steels_ Metallurgy and Applications, Third Edition

278 Steels: Metallurgy and Applications

A5

E

E

~4

~3

E

5 mm

Curve 290 m radius

Axle load 25 tonnes

O BS11 Normal grade

r 110 kg/mm 2 1% Cr grade

O O

0 5 10 15 20 25 30

MGT of traffic

Figure 3.42 Side wear in normal and 1% Cr rails under identical service conditions

(After British Steel 45)

BS 11 with the lowest hardness and tensile strength exhibits the highest wear
rate but this falls progressively to low values as the alloy content and hardness
of the materials is increased. However, whilst producing the correct order of
merit, this test exaggerates the relative performance of the various steels under
operating conditions and therefore laboratory rig testing has to be supplemented
by measurements of rail wear under normal track service. An illustration of
the development of side wear in BS 11 Normal and 1% Cr rails is given in
Figure 3.42. This indicates that 1% Cr material has a wear resistance of three to
four times that of BS 11 Normal under the particular track conditions identified
in this figure. Other track tests indicate that wear-resistant grades have twice the
resistance of BS 11 Normal.
Side wear of the type illustrated in Figure 3.42 is a function of axle load and
track curvature, the centrifugal force causing the flange of the wheel to scrub
against the gauge comer head of the high outer rail in the curve.

Austenitic 14% Mn rails

When the service conditions are such that exceptionally high rates of wear are

experienced in high-strength rails, then consideration is given to the use of rails

of the following composition which develop an austenitic microstructure:

C% Si% Mn%

0.75-0.9 0.2-0.4 13-14

The metallurgy of this material is complex but such steel has a very high resis-
tance to wear because of its high rate of work hardening when subjected to