Armour steel plate, or plate steel, is specifically engineered to withstand heavy impacts from high-velocity objects. It isn’t exclusively used in military applications, but armour is generally associated with security. Hence modern armour plating typically brings to mind the bulky superstructures of armoured fighting vehicles (AFVs), such as the British Challenger 2 battle tank or the EAGLE 4×4. Yet the most common visual representation of steel armour is the medieval plate suit. 

Medieval armour is routinely displayed in national heritage sites across Europe and has been immortalised globally through pop culture, cinema, and television. But the movies tend to focus on the aesthetic rather than the details. So, how did armour steel plate really work during the middle ages?

What is Medieval Plate Armour?

Medieval simply means related to the middle ages. Thus, medieval armour can literally refer to any piece of protective gear worn from the 5th to the 15th Century. The definition of what constitutes medieval armour is fairly murky given we are covering a period of roughly one thousand years–not to mention the enormous variation from region to region during that time. Consider that Western Europeans were developing the characteristic plate body armour we recognise today from about the 13th Century. In Japan, the iconic armour of the samurai was already in widespread use 100 years earlier.

That said, all forms of impact-resistant body armour were developed for the same reason: to prevent harm to the wearer. So, the same basic principles apply, whether we’re discussing the protective plated armour of the Western gentry or the lamellar plating of the Eastern nobility.

How Plate Armour Works

The goal of plate armour is to negate the force of an incoming object; a projectile, a bludgeoning object, or a weapon with a sharp edge. Absorbing a shock or an impact load requires relatively high hardness, which equates to high deformation resistance, meaning the material is less likely to scratch or indent when impacted by an object of inferior or similar hardness. However, it also requires a significant measure of toughness, which determines a material’s ability to absorb energy without failure. Other contributing factors include material composition, density, elasticity, and microstructure. But hardness and toughness are the two main mechanical properties determining how well steel will resist an impact.

It is important to note that most of the traditional tests used to characterize material properties were developed after medieval plate armour was in use. That said, contemporary craftsman were exceptionally skilled at creating high-quality steel pieces that successfully resisted repeated impacts. Metallurgical understanding naturally evolved over the course of the middle ages, yielding countless critical innovations, including new alloys and forging techniques. The most common alloys used in Western Europe throughout the period include:

  • Carbon steel: A basic carbon-iron alloy with high strength and hardness, but it lacked the ductility of later alloys, making it brittle and prone to fracture.
  • Spring steel: A more complex low-alloy steel used during later medieval times. Comprised of medium-to-high-carbon contents with manganese and silicon, spring steel was preferable for its greater flexibility.
  • Pattern-welded steel: Often incorrectly referred to as Damascus steel, this grade refers to the combination of two or more steels forge-welded into a single piece. It creates a highly distinctive pattern and was ideal for fabricating sharp weapons given its unique ability to maintain a sharp edge. Pattern-welded steel was less common in armour fabrication, given the significant effort and cost of manufacturing.

Looking for More Information?

Metallurgical engineering today is a far cry from that of the middle ages. The same applies to the range of alloy-grade steels available to users, as well as the applications for armour steel plates. Although the defence industry is one of the world’s largest consumers of steel armour plating, the enormous impact-resistant capabilities of high-alloy steel are advantageous in earth exploration, mining, and more. If you would like to learn more, why not read our blog post on armour steel plate for hydrocarbon exploration? Or, contact a member of the Masteel team today for information on the different ballistic steels that we stock and supply.