 The heat treating of metals is an age-old process discovered in the days of the first blacksmiths. Forged or machined metals, although in the desired shape, often retain many undesirable characteristics. The metals can be stressed from the shaping/machining process, and can be prone to cracks and early failure. In addition, because soft metal is easier to shape, soft metals are often chosen for the machining process but are then too soft to use after the machining has been completed. By heat treating the metal, these unwanted qualities can be eliminated and desired changes in the metal's hardness, ductility and durability can be achieved.
Heat treating metals, in the simplest sense, consists of only two processes: heating and cooling. Here, however, the simplicity ends. Each metal and each metal alloy must be treated differently in the heat treating process. Critical temperatures must be held for exactly the right amount of time, and the length of the cooling process and the coolant must both be carefully controlled in order to create a metal with the correct physical characteristics. If a metal is cooled too quickly or too slowly, the wrong quench is used, or the temperature of the heating or tempering process is wrong, the metal could warp and fracture. Heat treating metals is a delicate process, often considered as much an art as a science, and it requires true expertise to be done correctly.
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