Military Grade Steel: Common Defense and Aerospace Steel Grades
Specialized steel grades are typically called on to perform in a broad variety of military and aerospace applications ranging from bomb lugs, to tank armor, to jet engine components. The key to success in these challenging operating environments is military grade steel (also known by related terms such as aircraft quality steel).
In this article, we provide an informational overview of military grade steel, explain what makes it different, and highlight some common grades of steel ready for military and aerospace needs.
What is military grade steel?
Military grade steel refers to the types and quality of steel used to meet the demanding performance and durability requirements of U.S. Department of Defense applications. Due to the closely related requirements of the aerospace industry, many of these same grades of steel may also commonly referred to as “aerospace grade steel” or “aircraft quality steel.”
Some of the challenging engineering requirements for military grade steel include:
In the case of ballistic steel, providing protection against the impact of projectiles and blasts.
Standing up to the extreme temperatures and operating conditions experienced by aircraft and missile components.
Providing exceptional durability and long life cycles for automotive and other mechanical components in rugged conditions.
Traceability.
While the Military uses many grades of steel for all sorts of applications, military grade steel refers specifically to the steel grades formulated to meet unique defense and aerospace requirements.
What makes military grade steel different from other common grades?
Military grade steel provides exceptional characteristics such as hardness, strength, durability, corrosion resistance, impact ballistic resistance and thermal resistance. To achieve these characteristics, military-grade steels often employ carefully engineered alloy content and heat treatment. Each type of military grade steel is defined by detailed specifications (ie. chemistry, cleanliness, impact resistance).
Military grade steel provides outstanding hardness, but not necessarily greater than that of commercial grade abrasion-resistant steel. Military grade steel’s true differentiators are their strict performance requirements and testing standards, essential for ensuring complete dependability. For example, these steels undergo unique ballistic limit testing, a controlled process for measuring the firing pattern and velocity needed to completely and partially penetrate a target made from the given steel.
Military grade steel can often be high cost due to high quality and requisite testing measures.
Military Grade Steel Specifications
We provide a general overview of a few representative military grade steel specifications below for informational purposes only. Jade-Sterling Steel is proud to certify all aircraft quality materials according to these qualifications, which apply to all of the grades outlined in this article.
AMS 6415
AMS 6415 is a particular specification for military grade SAE 4340. The steel has rigorous cleanliness, internal soundness, and surface microstructural requirements for exceptional toughness, abrasion resistance, impact resistance, and ability to withstand atmospheric corrosion. AMS 6415 steel can be found in demanding defense and aerospace applications ranging from landing gear to ordnance components.
AMS 6427
AMS 6427 is a specially modified 4330 steel. It can be heat-treated to withstand extreme environmental stress. Like AMS 6415, it also has rigorous cleanliness, internal soundness, and surface microstructural requirements. It also has demanding impact strength requirements, with high tensile strength with excellent impact properties, this specification is a common choice for structural components like airframes.
Common Defense and Aerospace Steel Grades
While not exhaustive, the list below highlights the variety of military grade steels, which allows them to be carefully matched to the needs of diverse defense and aerospace applications. For each of these grades, additional heat treatment and other surface finishing processes may be used to achieve the required characteristics for a given application.
4340 AQ
Generally, 4340 steel is a nickel-chromium-molybdenum alloy steel. These alloying elements increases the hardening that occurs during the oil quenching process. 4340 AQ offers:
High strength and toughness
Deep hardenability
Excellent ductility
Exceptional creep and fatigue resistance
The “AQ” in this designation refers specifically to “aircraft quality” specifications of this steel, typically specifying enhanced cleanliness produced via specialized refining. Common applications include bomb lugs, tie downs, and D rings.
4330 V Mod
4330V steel refers to an alloy steel with additional manganese, chromium, nickel, and vanadium compared to 4340 steel. These additional alloying elements help provide greater strength and hardness, and this grade is often employed specifically in shock and impact-absorbing components. Vandium provides enhanced strength and grain size stability.
Common applications for 4330V include landing gears, air frames, and fasteners.
HF1
HF1 steel refers to “high fragmentation” steel, a highly specialized formulation designed specifically for use in mortar shells and other ordnance designed to shatter into high-velocity fragments on impact to generate an expanded damage radius.
1340
An alternative to HF1, 1340 generates less fragmentation and damage, providing a cost-effective alternative in ordinance testing.
A Trusted Partner for Military and Aerospace Steel
Jade Sterling Steel offers a full array of value-added finishing processes needed to tailor military and aircraft quality steel to highly demanding applications, including rough turning, annealing, and saw cutting.
Our unique supplier relationships allow us to consistently offer these grades to spec on a regular basis, while our comprehensive supply chain even gives us the ability to fulfill large orders on a just-in-time basis, allowing customers to receive shipments as they are processed — a rare capability given the exceptional manufacturing and testing standards required by military grade steel.
We invite you to reach out to our defense steel expert Paul Maleski to learn more about sourcing the right steel for your project requirements.
About the Author
Paul Maleski
Paul J. Maleski is a Partner with Jade-Sterling, with 27 years of experience in the steel industry. Paul works with customers to provide a quality supply for large programs in all major markets, with a special focus on the forging industry. Paul is also Jade Sterling’s stainless steel expert.
Paul is a proud graduate of Mercyhurst University, where he played football and graduated with a bachelor’s degree in business administration in 1997, joining Jade Sterling Steel that same year. After decades of experience as a Sales Manager, Paul joined the Jade Sterling partnership group in 2024.
