Many grades of low-carbon steel are made to meet specific chemical standards.
While there are some chemical guidelines to military grades of steel -- such as a maximum carbon weight percentage of 0.32% -- military grade standards focus primarily on two factors: hardness and ballistic limit.
Hardness is represented by the Brinell Hardness Number (BHN), which is calculated by comparing the amount of applied force to the size of the indentation of the force on a piece of material.
Military grades of steel have a BHN that is two to three times higher than common low-carbon steel -- such as A36. The higher the BHN, the more abrasion-resistant the material, which is a critical characteristic of military steel.
Below is a chart that compares the BHN of standard low-carbon steel with military grade steels, as well as abrasion resistant steels.
|BHN Between Steel Grades|
|A36||Low-carbon steel||133 BHN|
|AR400||Abrasion Resistant||360-440 BNH|
|AR500||Abrasion Resistant||470-540 BNH|
|MIL-46100||Military Grade||477-534 BNH|
|MIL-46100||Military Grade||477-534 BNH|
|MIL-12560||Military Grade||330-410 BNH|
|MIL-46177||Military Grade||362 BNH|
Abrasion resistant grades of steel have similar or higher BHNs than military grades of steel, but the difference between AR and military grade steel is that military grades undergo ballistic limit testing.
Ballistic testing finds the velocity at which a target would completely penetrate and partially penetrate a target using a controlled projectile, firing pattern and velocity.
Once the material has been certified to meet military grade standards, the certification guarantees the ballistic limit and integrity of the material completely.
This certification is an important difference between abrasion resistant steel and military grades of steel. It comes at a cost -- military grade steel is about twice the price of abrasion resistant material -- but guarantees the material's integrity during combat.
Falling somewhere between abrasion resistant grades and military certified grades, commercial grade armor is certified to meet the National Institute of Justice (NIJ) standards 0101.06. These standards classify ballistic "threat levels" that the armor will protect against.
Slightly more expensive than abrasion resistant grades -- but less expensive than military certified grades -- engineers may opt for commercial grade armor for projects that require some ballistic protection, but not quite to the level of military combat. Examples include some bank vaults, armored cars for cash transportation and body armor.
While there are many types of military grades of metal materials, the most common steel grades are MIL-A-46100, MIL-A-12560 and MIL-A-46177.
MIL-A-46100 steel plate is typically used to stop hyper-velocity projectiles (HVPs) and sniper fire. This grade is available up to 2-inches in thickness, depending on the size and speed of the projectile as well as the distance the projectile is traveling.
MIL-12560 is a common military-specified armor used in a variety of defense applications, including:
Compared to other military grades, MIL-12560 absorbs shock very well. MIL-12560 must meet Fragment Simulated Projectile standards before being certified, and is available in four classes:
Class 1: Resistance to penetration
Class 2: Resistance to shock
Class 3: Testing and evaluation
Class 4: Maximum resistance to penetration
MIL-A 46177 is a less commonly requested grade. It has a max thickness of 0.249-inches and is primarily used for armor, liners or small vehicle applications.
We receive a lot of customer questions about whether there is a weight difference between each of the military grades. Weight is generally the same for all grades - the main difference between the grades come from properties and applications.
To determine the weight of a military grade, use our calculator.
Leeco® Steel maintains a deep supply of military grade, commercial grade armor and abrasion resistant steel plate. Learn more about our offerings or build your quote today.