AMS 6526 LESCALLOY Steel Round Bar, AMS 6526 Alloy Steel Rods, Bars(Nickel Cobalt Aircraft Armour)

Product Description

AMS 6526 is the primary, globally recognized SAE International specification for premium aircraft-quality HP 9-4-30 ultra-high-strength steel (commercially known as Lescalloy HP 9-4-30 Vac-Arc; UNS K91283).

While sibling specifications like Boeings BMS-7-182 Type 2 or McDonnell Douglass MM-S-2102 represent proprietary corporate standards, AMS 6526 is the overarching open commercial standard governing the production of this nickel-cobalt alloy. It is highly sought after in round bars, rods, and heavy structural bars for military aircraft armor protection, rocket motor casings, and hyper-stressed airframe parts.

1. Baseline Metallurgy & Premium Melting

To meet the rigid toughness constraints of AMS 6526, the material relies on a chemical matrix stabilized by massive additions of Nickel and Cobalt. It is typically melted via AOD (Argon Oxygen Decarburization) + VAR (Vacuum Arc Remelting) or premium double-vacuum VIM-VAR processes to isolate and destroy trace non-metallic impurities.

Nominal Chemical Composition (%)

• 7.5% Nickel: Ensures the steel retains a high level of plane-strain fracture toughness ($K_{Ic}$), preventing catastrophic brittle fracture even if the metal is pierced or shocked by ballistic ordnance.

• 4.5% Cobalt: Acts as a magnetic-like lattice matrix anchor. It elevates the core hardening temperature threshold, prevents tempering softening, and minimizes unstable retained austenite.

2. Supply Profiles: Round Bars, Rods & Bars

Under the standard AMS 6526 (specifically the current AMS 6526J revision) framework, products are conditioned for highly controlled, heavy industrial machining:

• Delivery Condition: Universally stocked and delivered in the Annealed state (or Normalized & Tempered depending on the sub-tier purchase order parameters). This optimizes initial chip-removal speeds, sawing, and drilling before deep heat-treating takes place.

• Common Dimensions: Available from cold-drawn precision rods starting around 0.375" (9.5 mm) up to heavy hot-rolled / forged round structural bars exceeding 8.5" (215 mm) in diameter.

• Acoustic Flight Safeguards: Materials sourced to this standard are almost systematically cross-certified to MIL-STD-2154 Class A ultrasonic testing, ensuring zero internal air micro-bursts, slag inclusions, or internal cooling cracks.

3. High-Performance Mechanics (Post Heat-Treatment)

The engineering advantage of AMS 6526 over standard ultra-high-strength materials (such as AISI 4340 or 300M) is its rare combination of 220+ ksi tensile strength matched with superb weldability.

• Ultimate Tensile Strength (UTS): 220,000 240,000 psi (1517 1655 MPa)

• Yield Strength (0.2% Offset): 200,000 psi (1379 MPa) minimum

• Elongation & Reduction of Area: ~14% elongation with a 4550% reduction in area, showcasing a massive plastic deformation window before terminal structural failure.

• Weldability Profile: Highly weldable via TIG/GTAW using filler wire of a matching composition. Unlike common high-strength aircraft steels, it does not suffer from chronic heat-affected zone (HAZ) embrittlement if handled via careful post-weld tempering.

4. Key Military & Defense Applications

• Aircraft Armour Shielding: Blast-containment bulkheads, cockpit ballistic panels, and fragmentation deflector guards surrounding jet engine turbine shrouds.

• Airframe Structural Hubs: Highly dynamic landing gear truck beams, primary wing-attachment pivot assemblies, and main fuselage carry-through structures.

• Aerospace Pressure Housings: High-pressure solid rocket motor casing segments and structural space vehicle isolation joints.