work hardening: improved tensile strength and hardness in the localised area when a metal is cold worked.
anealing: heating work hardened metal and very slowly cooling it, making it easier to work by making it less brittle and more ductile
Case hardening: a process for hardening the surface of steels with less than 0.4% carbon content
Carburising: changes the chemical composition of the surface of low carbon steel so it absorbs more carbon and increases surface hardening.
Quenching: rapid cooling of heat treated metal
Hardening and tempering: heating medium or high carbon steels to a given temperature , rapidly cool via quenching and then heating to a set temperature to remove excess hardening.
Tempering colour: the colour seen on metal that indicates the temperature at which brittleness is removed
Critical point: the temperature at which the atoms of carbon and steel mix freely before bonding together and becoming solid.