9311 Flat Rolled Products Foil Sheet and Plate

Flat rolled products are produced in rolling mills, where cylindrical rolls reduce the thickness and increase the length of ingot. The process begins with huge heated ingots 6 ft wide, 20 ft long, and more than 2 ft thick and weighing over 20 tons that are rolled back and forth in a breakdown mill to reduce the thickness to a few inches. Plate of this thickness can be heated, quenched, stretched (to straighten and relieve residual stresses), aged at temperature, and shipped, or may be coiled and sent on to a continuous mill to further reduce its thickness. Before further rolling at the continuous mill, the material is heated to soften it for cold rolling. Heat treatments and stretching are also applied there after rolling to the desired thickness. Alternatively, sheet can be produced directly from molten metal rather than ingot in the continuous casting process, by which molten aluminum passes through water-cooled casting rollers and is solidified. The thickness is then further reduced by cold rolling.

The resulting flat rolled products are rectangular in cross section and are called foil, sheet, or plate, depending on their thickness (Table 9.22). Foil has a thickness less than 0.006 in. (up through 0.15 mm). Sheet has a thickness less than 0.25 in., but not less than 0.006 in. (over 0.15-6.3 mm). Plate is 0.25 in. (over 6.3 mm) thick or more. The use of the term "flat" in flat rolled products is to distinguish these from rolled wire, rod, or bar, which are discussed in Section 9.3.1.3.

Foil is produced as thin as 0.00017 in. thick, in alloys 1100, 1145, 1235, 2024, 3003, 5052, 5056, 6061, 8079, and 8111, in both rolls and sheets, and in the annealed and H19 tempers. The H19 variety is called hard foil because it is fully strain hardened. Uses for foil include the cores of aluminum honeycomb panels used in aircraft, capacitors (ASTM B373 Foil for Capacitors), and for packaging

TABLE 9.22 Relative Cold Extrudability of Annealed Alloys

Alloy

Relative Cold Extrusion Pressure

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