ABSTRACT
A main battle tank track link, such as that fitted to Chieftain sketched right, is sand cast in 13%Mn Hadfield steel – with 1%C, and at first sight is perhaps a surprising choice. The high recoil force of any large gun puts considerable stress on the trail legs during firing, and their fatigue life is important, since several thousand firing cycles are expected without failure. This consideration combined with the requirement for air-portability led to the selection of ‘FV520’ ultra-high strength high alloy steel for these trail legs. During plastic deformation, face centred cubic austenitic steels give a higher rate of work hardening than body centred cubic ferritic or martensitic steels – as shown in the tensile curve. The weight is saved by constructing the trail and some other carriage parts in titanium alloy Ti-6Al-4V. However, titanium alloy Ti-6Al-4V is about three times the cost of FV520 steel per ingot tonne.
