Armor steel is a high-strength low-alloyed structural steel which has been processed to give high penetration resistance and blast protection. The steel’s properties are reached by quenching and tempering to reach the desired balance between hardness and toughness.
Armor steel properties make them more versatile than ceramic plate. They are easier to shape and install on different types of equipment that need protection against incoming projectiles and explosives.
The required protection performance naturally depends on the levels of threat. The harder the steel, the higher the protection level against ballistic and high-velocity projectiles. Although, high hardness makes the steel harder to process into any shape other than flat. That’s why all installations of ballistic steel plate have to consider hardness, toughness and thickness for the actual application.
Armor and ballistic steels areis used in a lot of application areas requiring additional protection, such as:
The main groups of bulletproof metal are blast protection steel and ballistic protection steel. They are both characterized by the steel’s tempered martensitic microstructure. They are usually certified according to military standards such as the NIJ standard.
Blast protection steel has a relatively low hardness of around 400 HBW (Brinell hardness) and is also tough in freezing conditions since it needs to absorb the energy of a blast without cracking. Rolled homogenous armor (RHA) belongs to this category.
Ballistic protection steel is classified according to its hardness. High hardness armour steel (HHA) with a hardness of around 500 HBW is the most common grade. They can be bent and welded and have good fatigue resistance. HHA with a thickness of 6.5 mm is usually enough to give protection against a NATO standard 5.56 mm calibre bullet SS109.
Next step up in hardness is very high hardness armor steel (VHH) with around 550 HBW. Despite its hardness it’s still bendable and weldable. 5.5 mm thick VHH steel will usually be adequate to stop a NATO standard 5.56 mm calibre bullet SS109.
Moving further up in hardness we have ultra-high hardness armor steel (UHH) and extreme high hardness armor steel (XHH) with hardness of 600 HBW and 650 HBW. These steels give additional protection against projectiles at the expense of bendability and other forms of processing. Bending and welding of the XHH grades are generally not recommended.
One way to increase protection and reduce weight at the same time is to mount two thinner armored steel plates with a space between them instead of one thicker plate. The combined weight of the two plates can be 25% less than the single plate, depending on the desired protection level, the thicknesses of the plates, and the spacing between the plates.
Spaced installation can also be performed with a perforated outer plate. The perforations in this plate are made to be smaller than an expected projectile and slow it down enough to make it lose its penetrating power.
SSAB manufactures a wide range of armor steel under the names Armox® and Ramor®. Both grades protect all kinds of applications in low to severe threat environments. Armox® and Ramor® are used for vehicles, buildings, ships, safe rooms, infrastructure installations and other objects that need enhanced protection.
British Armour Inc., a global manufacturer of armored SUVs with certified advanced ballistic protection, chooses a leading armor steel plate to protect its vehicles.
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