Hardened materials are usually tempered or stress relieved to improve their dimensional stability and toughness. Steel parts often require a heat treatment to obtain improved mechanical properties, such as increasing increase hardness or strength.
In this manner, how do you harden steel at home?
Heat the entire piece of steel slowly at first. Then, concentrate the heat on the area that is to be hardened, such as a chisel point or screwdriver blade tip, until that area glows red hot. Quench the steel in a fluid. Dipping the hot steel into a liquid or gas rapidly cools it, hardening the metal.
What temperature does steel turn blue?
Steel in a tempering oven, held at 205 °C (401 °F) for a long time, will begin to turn brown, purple or blue, even though the temperature did not exceed that needed to produce a light-straw color.