Air Force

Low Alloy, High Impact Toughness Steel

Strength & toughness without expensive alloys. Superb material properties at -40C even in thick sections. In use by DoD.

Materials
The US Air Force Seeks to commercialize a tungsten free, low alloy steel with the strength, ductility and impact toughness at sub-zero temperatures equivalent to steels that cost several times more.

Typical Composition of USAF-96 Steel

The U.S. Air Force Research Laboratory at Eglin AFB has developed and scaled up to 200,000lb+ quantity USAF-96 Steel. USAF-96 Steel is a low alloy steel that when thermally processed with the inventive method 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 @ -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” in thickness.

Steels with this combination of performance usually contain significant amounts of tungsten (W), cobalt (Co), and/or nickel (Ni) – these are amongst the most expensive alloying elements. Moreover, W is difficult to process and complicates the waste streams; 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 lead 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.

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