What's The Tempering ?

           Will be reheated after hardening of the workpiece to the appropriate

temperature below the lower critical temperature,heat preservation for a period

of time after cooling in air or water,oil and other medium metal heat treatment

process.Or will the alloy after quenching of heating to proper temperature,heat

preservation several time,and then slowly of fastcooling.Commonly used to reduce

or eliminate internal stress of hardened steel,or reduce the hardness and strength,

in order to improve the ductility and toughness.