Heat Treating Metal
Heat treating metal is a process that is used to harden or soften metals by heating and cooling them until the desired properties are reached. Heat treatment can alter the physical, chemical, structural and mechanical qualities of the metals. Some commonly heat treated metals include aluminum, titanium and magnesium, although steel is by far the most commonly heat treated metal.
Heat treating is an energy-intensive process that changes the internal atomic structure of the metal being heated. This is accomplished through heating and cooling processes. This can be accomplished using either raw material or pre-formed parts. Some common treatments employed during heat treating include annealing, quenching, case hardening, precipitation strengthening, normalizing and tempering. Annealing, the slow cooling of metal, transforms small grains into larger grains and results in a soft, ductile metal. Quenching, which refers to the rapid cooling of metal, can be used to increase a metal's strength. Case hardening creates a tough outer coating that surrounds a softer more malleable core by combining the ductility of low carbon materials with the strength of high carbon. Precipitation strengthening, also known as age hardening, is a process used to increase the yield strength of the metal. Normalizing erases the effects of any previous heat treatment. Tempering is the reheating of metal to reduce brittleness and increase the metals hardness. There are countless other heat treatments, including but not limited to, homogenizing, stabilizing and stress relieving. All of these improve the quality and form of the metal.
Along with improvements to hardness and ductility, significant increase and reductions can be made to the metals tensile, impact and yield strength qualities. Although heat treatment is most commonly used in changing the physical, chemical, and mechanical structures of metals, the treatment can also be applied to ceramics, glass and polymers. Many different kinds of equipment are used during the heat treating process. Some of these tools include furnaces, torches, salt bathes, heating blankets, and lasers. Industries that use heat treatments with metals include: automotive, construction, military, tool and die, shipping, transportation and aerospace. Some examples of heat-treated metal goods include car doors, airplane wings, swords, musical instruments, and metal machine components. Using heat treatment to produce parts makes the products more capable of performing the requirements necessary in their industrial applications.