Materials for engineering, 3rd Edition - (Malestrom)

Metals and alloys 103
Turbine entry temperature (K)
2100
1900
1700
Uncooled
blades
Cooled
blades
Coated
blades
Demonstrator
technology
Production
technology
Trent
1500
Conway
RB211
1300
Spey
SC cast
1100
W1
Dart
DS cast alloys
Conventional cast alloys
Avon
900
Wrought alloys
1940 1960 1980 2000 2020
Date
3.20 Increase in gas turbine entry temperature since 1940.
(Courtesy of Messrs Rolls–Royce Limited.)
3.2.8 Steels
We will approach our consideration of this large group of engineering alloys
by dividing it into three sections: low-carbon steels, engineering steels and
stainless steels.
Low-carbon steels
The iron–carbon phase diagram is shown in Fig. 3.21. We may arbitrarily
describe low-carbon steels as those containing no more than 0.2% carbon.
Their microstructure will thus be essentially ferrite (α) with a small volume
fraction of carbide (Fe 3 C) often present as the α/Fe 3 C eutectoid (pearlite).
The lower end of this range of carbon content (i.e. very low carbide content)
is mainly applicable to steel in the form of thin strip and the upper end to
structural steel in the form of thicker plates and sections.
Strip steels
Strip steels are manufactured by hot rolling to thicknesses not less than 2
mm, and then finally cold rolled to the required final thickness. Since cold
forming (e.g. by deep drawing, stretch forming or bending) is a widely used
application for low-carbon strip steels, a final recrystallization anneal is
applied. Considerable processing expertise is required to optimize the grain
size, the crystallographic orientation (‘texture’) of the grains and the solute
(C and N) content in order to enhance the formability of the strip. The
presence of a strong yield point is undesirable, as the irregular flow may lead