6061 Aluminum is a ductile metal that can be stamped, cut, deep drawn, drilled, tapped, bent, welded, hydroformed, and more. Magnesium and silicon are the main alloying elements in this metal, and 6061 is generally strong and corrosion resistant. It is heat treatable and resistant to cracking when stress relieved. When 6061 aluminum comes off the shelf, it is usually in the O state, which is its softest, most pliable state. During the forming process of some aluminum parts, customers require a heat treatment process to soften and relieve stress on the part to avoid vibration problems and maintain the shape of the part.
The process of bringing a 6061 aluminum part to a stronger, more durable condition in the O temper begins with heat treating the part at 985 degrees Fahrenheit for one hour in a lowering furnace. At this point, place the basket with the parts in the quench tank. Quench liquid is circulated to rapidly cool components. Key to this process is speed and uniform cooling; parts are quenched within 6 seconds of opening the bottom-bottom furnace door.
Through this process, the quenched aluminum part is now in the W temper. In this case, the material can be shaped or straightened. Because time and room temperature air can also have a hardening effect, leaving these freshly treated aluminum parts in the open air on the shop floor for 96 hours will bring the part to a T4 hardness. 6061-T4 aluminum is the hardest part this aluminum alloy can get. The aluminum hardening process can be stopped by placing the aluminum parts in the freezer until they are ready to be hit again on the press.
After secondary pressing, the parts undergo an aging heat treatment process. The aging time for 6061 aluminum is between 350 and 500 degrees Fahrenheit, and the part stays in the oven for 12-24 hours depending on thickness and other factors.
After this aging, the part is now in T6 condition. In general, T6 is a common temper for aluminum, as 6061 aluminum is often used in heavy construction where the metal is in that temper where strength and limited formability are important.