| Property | Requirement | |----------|--------------| | Tensile Strength | ≥ 220 ksi (1517 MPa) | | Yield Strength (0.2% offset) | Typically ≥ 180 ksi (varies by alloy) | | Elongation in 4D | ≥ 6% (typical minimum) | | Reduction of Area | ≥ 20% (typical minimum) | | Hardness (HRC) | Approx. 48–55 HRC (depending on exact strength level) |
This essay provides a detailed examination of AMS 2759-2, exploring its scope, its rigorous requirements for pyrometry (temperature measurement), the nuances of its heat treatment cycles, and its broader implications for quality assurance in the aerospace supply chain.
As-quenched steel is extremely hard but brittle. AMS 2759-2 mandates tempering to relieve stresses and achieve the final mechanical properties. The specification requires tempering to commence within a specific timeframe after quenching to prevent delayed cracking (a phenomenon where internal stresses cause the part to crack spontaneously at room temperature). ams 2759 2
Furthermore, the atmosphere within the furnace must be controlled to prevent:
The standard is specifically geared toward "parts" rather than raw "stock." This means it applies to components that have been machined or formed into their near-final shapes, where dimensional stability and surface integrity are paramount. 2. The Process Sequence AMS 2759-2 mandates tempering to relieve stresses and
These materials are used where a combination of high strength, toughness, and fatigue resistance is essential.
AMS 2759-2 imposes strict limits on decarburization depth. It requires the use of protective atmospheres (such as endothermic gas or nitrogen-based systems) or vacuum furnaces. If decarburization occurs, the specification provides limits on how much material may be removed by machining post-heat treatment, or conversely, how much carbon may be restored via "carbon restoration" cycles (though this is generally less preferred due to complexity). exploring its scope
The specification sets time and temperature parameters based on the specific steel grade (e.g., 4130, 4340). It specifies minimum soaking times—how long the part must dwell once the coldest part of the load reaches the target temperature. This ensures the crystalline structure fully transforms into austenite. A unique feature of AMS standards is their conservative nature; they often mandate longer soak times than commercial standards to ensure through-thickness transformation in varied geometries.
The ultimate pass/fail criteria for AMS 2759-2 is often mechanical testing. The specification defines hardness requirements, typically using the Rockwell C scale (HRC). It details sampling plans—how many parts per lot must be tested to statistically validate the batch.
This "slash specification" works in tandem with the general AMS 2759 requirements, adding the rigorous controls needed for ultra-high-strength components. The Scope: Who is AMS 2759/2 For?