High-strength quenched and tempered steels offer design engineers a number of advantages that can be used as solutions to everyday and difficult or unusual engineering problems. In some cases, mass savings of up to 30% or more are possible for specific types of primary structural steel work. Longer spans, greater load-carrying capacity and net weight reduction to reduce foundation loads are all possible through the use of higher-strength (up to 690 MPa yield strength and beyond) steel plate. The use of high-strength steels in Australia over the last 20 years or more has predominantly focused on the mechanical engineering space, with the recent resources boom providing ample scope for its use in equipment such as dump truck bodies, storage bins, hoppers and chutes, where lighter weight, wear resistance and impact resistance, combined with straightforward fabrication, has facilitated ready adoption. These same benefits can extend to certain applications in the structural engineering space.

Contemporary high-strength Q&T steels are all generally considered low- to medium-alloy content steels, exhibiting high strength and hardness, coupled with good formability and weldability. They also maintain exceptionally low temperature notch toughness and crack propagation resistance despite the high strength levels involved. This unique combination of properties is the result of careful selection of both chemical composition and heat treatment.

Principal alloying elements in modern Q&T steels are nickel, manganese, chromium, copper and molybdenum, with additional hardening often being provided by smaller but more precisely controlled additions of boron (typically 0.002% B). These elements are often used in combination, such that Q&T steels can be classified as multiple low–medium alloy heat-treated steels.

Most Q&T steels also incorporate one or more micro-alloying elements such as aluminium, niobium, titanium, vanadium or zirconium. Vanadium bearing steels should be avoided if post-weld heat treatments are to be employed due to the possibility of adverse effects on the heat-affected zone (HAZ) notch toughness.

Specific composition ranges for each element are adjusted, to the extent that steel specifications might allow, by the steel manufacturer according to strength and other property requirements, and to provide the necessary hardenability. Comparatively higher alloy contents are required in thicker plates to offset the retardation in cooling rate that inevitably accompanies quenching of the heavier plate sections.