AMS 6487
AMS 6487 is the SAE Aerospace Material Specification for H11 (AISI H11) chromium hot-work tool steel in the bar, forging, and mechanical tubing product forms. H11 (4.75–5.25% Cr, 1.10–1.60% Mo, 0.30–0.60% V, 0.33–0.43% C) achieves tensile strengths of 280,000–320,000 psi in the quenched and tempered condition — comparable to 300M — but with dramatically higher impact toughness (Charpy V-notch 15–30 ft-lb at 48–52 HRC versus 8–12 ft-lb for 300M at equivalent hardness). This toughness advantage makes H11 the material of choice for aerospace bolt applications at the 280 ksi strength level and for die casting and forging dies subject to severe thermal and mechanical shock loading.
H11 is air-hardening — it hardens to full through-section hardness during air cooling from the austenitizing temperature without oil or water quenching, eliminating the quench cracking and distortion risk associated with quench-hardened steels in complex-shaped parts. AMS 6487 covers the standard-grade (air-melt or electroslag remelt) product; the premium VAR grade is covered by AMS 6488.
H11 to AMS 6487 heat treated at 1825–1875°F austenitizing temperature and double-tempered at 1000–1050°F achieves 280,000 psi UTS with HRC 48–50 and Charpy V-notch 15–30 ft-lb. This extraordinary toughness at 48–50 HRC distinguishes H11 from all conventional structural alloy steels, which typically exhibit 2–5 ft-lb at equivalent hardness. The high Cr-Mo-V composition provides secondary hardening during tempering — the hardness actually increases on the first temper before dropping to the final level, requiring a mandatory double or triple temper to stabilize the microstructure.
- Aerospace bolts and fasteners at 280,000 psi strength level
- Die casting dies for aluminum and magnesium alloy components
- Forging dies and punches for aerospace part production
- Aircraft structural pins and clevises at extreme load
- Hypersonic vehicle structural members at elevated temperature
- Nuclear application components requiring toughness at high hardness
AMS 6488 — H11 Premium Bar
Premium VAR H11 tool steel bar with maximum cleanliness for fatigue-critical fasteners and aerospace structural forgings.
AMS 6257 — 300M Bar
Si-V modified 4340 at 280 ksi minimum for aircraft landing gear — the standard ultra-high-strength structural steel worldwide.
Certified Material for Critical Service
AMS 6487 certifications include chemical composition per heat, mechanical properties per lot (tensile, yield, elongation, Charpy impact, and hardness), annealed hardness maximum, grain size, and inclusion rating per AMS 2301. For fastener applications, additional requirements from the applicable fastener specification (NAS, AN, or MS) regarding head forming, grain flow, and ultimate load testing apply. Full heat-lot traceability is maintained.