AMS 6484
AMS 6484 is an alternate SAE Aerospace Material Specification for SAE 4340 air-melted nickel-chromium-molybdenum alloy steel in the bar and forging product forms. While sharing the same nominal 4340 composition as AMS 6415 (1.65–2.00% Ni, 0.70–0.90% Cr, 0.20–0.30% Mo, 0.37–0.44% C), AMS 6484 covers different heat treatment conditions and property levels suited to applications requiring tensile strengths in the 200,000–220,000 psi range with improved fracture toughness relative to the higher-strength AMS 6415 conditions.
AMS 6484 is selected in design applications where the structural analysis permits 200,000–220,000 psi rather than the maximum 260,000 psi of AMS 6415, trading some ultimate strength for improved ductility, fracture toughness, and reduced hydrogen embrittlement sensitivity — particularly important for components that will be electroplated (cadmium, zinc, or chrome plating) or processed in hydrogen-generating environments. Its fracture toughness at 200 ksi is typically 70–90 ksi√in versus 50–60 ksi√in for AMS 6415 at 260 ksi.
AMS 6484 material heat treated to the 200,000 psi condition achieves minimum 200,000 psi UTS with minimum 14% elongation and 50% reduction of area — substantially higher ductility than AMS 6415 at 260 ksi (8% elongation). The higher tempering temperature used to achieve the 200 ksi condition (typically 700–900°F versus 325–400°F for 260 ksi) eliminates the tempered martensite embrittlement zone, significantly reducing susceptibility to hydrogen-assisted delayed fracture after plating.
- Aircraft structural forgings at 200,000 psi design allowable
- Landing gear fittings where fracture toughness governs over absolute strength
- Electroplated structural components requiring hydrogen embrittlement resistance
- Aerospace actuator piston rods and clevises
- Bolts and fasteners in the 200 ksi strength range
AMS 6415 — 4340 Air Melt Bar
Standard 4340 bar and forging specification for primary aerospace structure at 200–260 ksi — the most widely specified high-strength structural alloy steel.
AMS 6411 — 4330 Bar/Forging
4330V Ni-Cr-Mo-V alloy — superior fracture toughness at equivalent strength levels for damage-tolerant landing gear design.
Certified Material for Critical Service
AMS 6484 certifications include chemical composition per heat, mechanical properties per lot in the specified heat treatment condition, grain size, and inclusion rating per AMS 2301. The applicable tempering temperature range and the resulting strength condition must be documented in the material certification. Full traceability by heat and lot is maintained per AS9100 requirements for aerospace structural material.