Low-Alloy, High-Impact-Toughness Steel

Air Force Research Laboratory, Eglin Air Force Base, Florida

USAF-96 Steel is a low-alloy steel that, when thermally processed with the method described here, has the following typical values: an ultimate tensile strength of 245 ksi, yield strength at 0.2% offset of 187 ksi, elongation to failure of 13%, and an impact toughness as measured with a Charpy V-notch test at -40 °C of 30 ft-lb. Of particular benefit is the through hardenability and toughness, which has demonstrated strength and toughness at -40 °C, even with sections up to 4” thick.

A tungsten-free, low-alloy steel has the strength, ductility, and impact toughness at sub-zero temperatures equivalent to steels that cost several times more.

Steels with this performance usually contain significant amounts of tungsten (W), cobalt (Co), and/or nickel (Ni) — among the most expensive alloying elements. Moreover, W is difficult to process and complicates the waste streams, and most high-performance Ni-Co alloys require expensive vacuum-induction-melting/vacuum-air-remelting (VIM-VAR) techniques.

USAF-96 Steel contains no W or Co, and is a low-carbon, low-Ni alloy steel composition. In addition to its material cost advantage, USAF-96 Steel can be produced using standard “air-melt” production processes at a substantially lower cost than prior methods. Its material composition along with specific thermal processing conditions leads to the growth of beneficial nano-scaled carbides in a martensitic matrix that allows USAF-96 Steel to possess its high-performance characteristics even in heavier sections while using reduced quantities of expensive alloying elements.

Applications may include penetrators, ground-engaging tools, and oil and gas applications. It is compatible with air-melt production, e.g. vacuum-degassed open ladle and argon-oxygen decarburization. It is also amendable to sand/investment casting followed by hot isostatic pressing and forging processes.

For more information, contact Joan Wu-Singel at This email address is being protected from spambots. You need JavaScript enabled to view it.; 406-994-7705.