This image taken from Raw to Ready: Mack Truck demonstrates how manganese was used to strengthen steel. Manganese is a chemical element found in many minerals. For industrial purposes, it’s normally used as an alloying agent with other metals. For steel, its added to increase toughness, which is the metal’s ability to deform without fracturing. The way manganese toughens metal is called twinning. Unlike mild steel, the layers are able to change position together. This allows the metal to deform more quickly, absorbing kinetic energy instead of breaking.