Aluminum Heat Treating
Aluminum heat treating is a process used to harden or soften aluminum by heating or cooling it until the desired level of hardness is reached. Heat treating is an energy-intensive process. In aluminum, the structure and composition of the grains determines the overall mechanical qualities of the metal. This internal atomic structure changes when it is heated; this changes the metal’s mechanical behavior.
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Applications of Aluminum Heat Treating
Aluminum is valued for its light weight and its resistance to corrosion. Because of these characteristics, aluminum and aluminum alloys are especially important to the aerospace, automotive and other transportation industries. These industries require many different shapes of aluminum that can be achieved through heat treating, and the demand for fabricated aluminum products is very high. Products include car doors, rocket bodies, storage tanks, aircraft panels and ventilation systems.
Methods of Aluminum Heat Treating
Aluminum sheet metal is made from slabs and rods of aluminum and aluminum alloys. These are melted and pressed into rectangular shapes. This sheet metal is found in four common grades: 1100-H14, 3003-H14, 5052-H32, and 6061-T6. The metal also ranges in thickness, which is measured in gauges. The range is roughly 8 to 30 gauges; the higher the number, the thinner the metal. This means that it can be as thin as foil or as thick as rods.
Several important techniques are used in the heat treating process, including:
- Annealing
- Quenching
- Case Hardening
- Precipitation Strengthening
- Tempering
Annealing is a process by which a metal is heated and then cooled very slowly, leaving the metal soft and ductile. Quenching refers to the rapid cooling of metal; it can be used to increase the strength of metal. Tempering, in contrast, is performed to strengthen stainless steel. During the tempering process, the metal is heated to extreme heat (between 400 and 600 degrees Celsius) and maintained at this temperature until the carbon diffuses to produce bainite or pearlite. Case hardening combines the ductility of low carbon materials with the strength of high carbon through the creation of a tough outer coating, which surrounds a softer more malleable core. Precipitation strengthening, also known as age hardening, is a process used to increase the yield strength of the metal. Many different kinds of equipment are used in the heat treating process. Some of these tools include furnaces, torches, salt bathes, heating blankets, and lasers.