Steels_ Metallurgy and Applications, Third Edition

264 Steels: Metallurgy and Applications

Table 3.17 Applications for maraging steels 32

Aerospace Tooling and machinery Structural engineering

and ordnance

Aircraft forgings (e.g.

undercarriage parts,

wing fittings)

Solid-propellant missile

cases

Jet-engine starter

impellers

Aircraft arrestor hooks

Torque transmission

shafts

Aircraft ejector release

units

Punches and die bolsters

for cold forging

Extrusion press rams

and mandrels

Aluminium die-casting

and extrusion dies

Cold-reducing mandrels

in tube production

Zinc-base alloy die-casting

dies

Machine components:

gears

index plates

lead screws

Lightweight portable

military bridges

Ordnance components

Fasteners

used selectively in applications where weight saving is of paramount importance
or where they can be shown to be more cost-effective than low-alloy grades. Some
typical uses for maraging steels are listed in Table 3.17. As one might anticipate,
these steels are used to advantage for weight reduction in aerospace and military
applications but their excellent combination of properties, ease of heat treatment
and dimensional stability also offer attractions in the more commercial sector of
tooling and machinery.

Steels for steam power turbines

Electricity is generated on a large scale by the following sequence of operations:

1. The production of steam at high temperature and pressure in fossil-fired boilers
   or nuclear reactors.


2. The passage of the steam through a turbine where it impinges on the blades
   of a rotor, thereby creating rotational energy.


3. The transmission of the energy developed in the turbine rotor to a generator
   rotor which produces electricity in the windings of the stator.

The rotor shafts in the turbine and generator are produced from very large, high-
integrity forgings which operate at speeds of about 3000 rev/min and over a range
of temperatures, depending on their position in the power train. In a typical
660 MW coal-fired station, the turbine has three stages, namely high pressure
(HP), intermediate pressure (IP) and low pressure (LP), and the last stage can
involve two or three cylinders. On the other hand, the turbines for large water-
cooled reactors operate at 1200 MW and involve only the HP and LP stages
with very large rotors. This is illustrated in the data in Table 3.18 by Collier