KAB steels are a newly developed grade of advanced ultra high strength steels, which distinguish
themselves by the rapid formation of fine nanostructured carbide free lower bainite. The term
nanostructured is used with respect to the thickness of the individual bainitic ferrite plates which can
vary between 50 nm to as fine as a few nanometers, depending on the temperature at which it was
formed. This enables these steels to obtain desirable combinations of mechanical properties due to the
presence of finely dispersed retained austenite which has been sufficiently stabilized via the formation
of bainite under conditions where the precipitation of cementite is suppressed. Under the influence of
stress and strain the retained austenite transforms into martensite and gives rise to microstructural
hardening (Transformation induced plasticity effect), enabling such steels reasonable values of
predominantly uniform elongation at strength levels of 2800MPa or higher. The aim of the current
work is to present the concept of KAB steels, and the relations between their microstructure and
mechanical properties. The feasibility of large scale industrial production of the new steel in also
discussed.
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