A high carbon steel called C75 has a carbon percentage of roughly 0.70-0.80%. Due to its capacity to be hardened and tempered to create springs with exceptional elasticity and endurance, it is frequently referred to as spring steel. Manufacturing of springs, saw blades, cutting tools, and other items requiring high strength and resistance to wear and fatigue frequently uses C75.

51CrV4 is a high carbon and chromium-vanadium alloy steel, on the other hand, with a carbon content of roughly 0.50–0.60%. It is also referred to as 1.8159 steel or 50CrV4. In comparison to C75 steel, 51CrV4 steel has better hardenability, toughness, and fatigue resistance thanks to the addition of chromium and vanadium. Coil springs, torsion bars, leaf springs, and other components for the automotive and aerospace industries that need high strength and exceptional fatigue resistance are frequently made from 51CrV4.