We heat treat metals in an attempt to optimise the mechanical and physical properties for a given application. Most people think of heat treatment as a process for hardening metal. This is not necessarily so, as many heat treatments are applied to soften metal in order to allow metal working operations such as deep drawing, cold forging and machining.
Where increased strength and wear resistance is required, hardening and tempering treatments are given. Extremely hard steels find applications in cutting tools where highly defined edges must be maintained and heat treatment of these steels is a critical operation. Hard surfaces with ductile base material may be developed by heat treatment.
There are also the solution heat treatments and ageing processes designed to increase the strength of some non ferrous metals and precipitation hardening steels.
Heat treatment is a significant industry and forms a basic part of the industrial infrastructure of countries.