How does steel differ from pure iron in strength and hardness?

In its pure form, iron is soft and lacks the necessary properties for most engineering applications. Steel differs from pure iron primarily through the addition of carbon, which significantly increases its strength and hardness.1

The hardening effect is demonstrated by comparing their diamond pyramid hardness (DPH) values. While pure iron has a DPH of approximately 70, steel containing pearlite can reach a DPH of 200 or higher depending on its carbon content.1

Beyond carbon, steel is further strengthened through alloying. Elements such as nickel or manganese increase strength by blocking the movement of dislocations within the metal's crystal lattice, a process known as solution hardening. Additionally, techniques like precipitation hardening and grain refinement further restrict dislocation flow, allowing for the creation of high-strength materials that are far more durable than pure iron.2