AMS 6524 LESCALLOY Steel Round Bar, AMS 6524 Alloy Steel Rods, Bars(Nickel Cobalt Aircraft Armour)

Product Description

AMS 6524 is an aerospace-grade, ultra-high-strength structural alloy steel specification established by SAE International. It covers the proprietary alloy HP 9-4-30 (commercially engineered by Latrobe Steel under the brand name Lescalloy HP 9-4-30; UNS K91313).

Designed primarily for critical defense and aerospace applications, it is famous for its role in aircraft armor plating, structural framing, and missile components due to its unparalleled combination of high fracture toughness, deep through-hardening capability, and ballistic impact resistance.

1. Material Chemistry & The Premium Melting Process

The suffix "9-4-30" indicates its base chemistry: 9% Nickel, 4% Cobalt, and 0.30% Carbon. The unique inclusion of cobalt prevents the steel from softening during high-temperature tempering and limits the formation of retained austenite.

To guarantee extreme micro-cleanliness and eliminate non-metallic inclusions that could act as fatigue crack initiation sites, AMS 6524 is produced exclusively using premium Consumable Electrode Vacuum Melting processes, such as Vacuum Induction Melting followed by Vacuum Arc Remelting (VIM-VAR).

Nominal Chemical Composition (%)

2. Forms of Supply: Round Bars, Rods, and Bars

While the baseline AMS 6524 specification historically emphasized flat-rolled forms (sheet, strip, and plate used directly for armored ballistic shields), manufacturers process the identical HP 9-4-30 VIM-VAR chemistry into bar stocks to satisfy structural fabrication requirements.

• Condition of Supply: Typically supplied in the annealed condition to maximize machinability, shearing, and bandsaw cutting efficiency before heat treatment.

• Size Configurations: Round bars and rods are commonly produced in diameters from 10 mm up to over 200 mm to accommodate heavy structural machining.

• Surface Treatments: Available in hot forged, hot rolled, cold drawn, centerless turned/peeled, or bright polished finishes depending on structural tolerances.

• Quality Controls: Products must adhere to premium aircraft-quality inspection standards, including rigorous ultrasonic testing and magnetic particle inspection (such as AMS 2300).

3. High-Performance Mechanics

What sets HP 9-4-30 apart from standard high-strength steels (like AISI 4340 or 300M) is its capability to maintain exceptional fracture toughness ($\mathbf{K_{Ic}}$) at yield strengths exceeding 200 ksi. It is specifically engineered to resist catastrophic fracture under explosive or ballistic shock.

Typical Mechanical Properties (Heat Treated)

• Ultimate Tensile Strength (UTS): ~220240 ksi (15161655 MPa)

• Yield Strength (0.2% Offset): ~200215 ksi (13791482 MPa)

• Elongation at Break: 10% 15%

• Typical Hardness: 4448 HRC

• Weldability: Unlike many high-strength alloys that suffer from heat-affected zone (HAZ) cracking, AMS 6524 offers good weldability in the annealed state, requiring post-weld heat treatment to develop full structural performance.

4. Primary Applications

• Aircraft Armor: Critical cockpit and engine ballistic shielding designed to defeat projectile impact.

• Structural Aerospace: High-stress structural aircraft framing, landing gear components, engine mounts, and fasteners.

• Defense & Space: Rocket motor casings, pressure vessels requiring through-hardening to high strength levels, and military missile structural rings.