The carbon in typical steel alloys may contribute up to 2.1% of its weight. Varying the amount of alloying elements, their formation in the steel either as solute elements, or as precipitated phases, retards the movement of those dislocations that make iron so ductile and weak, and thus controls qualities such as the hardness, ductility and tensile strength of the resulting steel. Steel’s strength compared to pure iron is only possible at the expense o ductility, of which iron has an excess.

Above you may find a diagram of the different procedures to create steel and its products.