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).
The specification mandates rigorous sensor placement and records, ensuring that when the controller reads 1,500°F, the part in the back corner of the furnace is actually at 1,500°F. Without this pyrometric rigor, the metallurgical instructions of 2759-2 would be theoretical at best. ams 2759 2
| 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) | As-quenched steel is extremely hard but brittle