How does manganese improve the strength and hardness of steel?

Manganese acts as a vital alloying agent that enhances the physical properties of steel, specifically its strength, hardness, hardenability, and abrasion resistance.1

It improves these characteristics through several mechanisms:

• Hardenability: Manganese slows the diffusion of atoms through iron lattices, which delays allotropic transformations. This allows for the formation of hard microstructures like martensite at lower cooling rates, resulting in a deeper hardened zone within the steel.2
• Strength and Ductility: In low-alloy steels, manganese increases yield and tensile strength. It also permits tempering at higher temperatures, which helps maintain better ductility while achieving high levels of strength and hardness.12
• Work-Hardening: In high-manganese alloys like Hadfield steel (containing 10 to 14 percent manganese), the metal exhibits exceptional wear resistance. This is due to its capacity for work-hardening, where deformation or pounding of the surface creates lattice disturbances that block the movement of dislocations, effectively making the steel stronger as it is used.13

Additionally, manganese improves steel quality by acting as a desulfurizer and deoxidizer, removing impurities that would otherwise compromise the metal's structural integrity.14