Carburizing is a case hardening process that introduces carbon into a solid ferrous alloy. This is accomplished by heating the metal in a carbonaceous atmosphere above transformation temperature for a pre-determined time. Subsequent to carburizing, parts are quenched to harden the surface carburizing layer. The core remains unaffected.
It is a widely used surface hardening process for low carbon steel. The industrial importance of carburizing is expressed in its market share, as one third of all hardening heat treatment is covered by carburizing and hardening.