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Sheet and Plate

When aluminum is passed between rolls under pressure, it becomes thinner, and longer in the direction in which it is moving. This simple process is the basis for aluminum’s most widely used forms: plate, sheet, and foil.

Aluminum can be flat-rolled and re-rolled until it reaches the desired thickness or gauge. Where the rolling process is stopped determines whether the final product will be plate (a quarter-inch thick or more), sheet (.249 to .006 inch), or foil (less than .006 inch).

The Production Process

Rolling begins with huge sheet ingots weighing as much as 20 tons, which have been preheated to make them easier to shape. As the size of rolling mills has increased, so has the size of these ingots, but a typical ingot is about six feet wide, 20 feet long, and more than two feet thick.

The ingot is first fed into a breakdown mill where it is rolled back and forth, reversing between the rolls until the thickness has been reduced to just a few inches. At this point, some plate is removed and readied for shipment. The plate is heat-treated and quickly cooled, or quenched, for added strength, and then stretched to straighten and to relieve internal stress built up during rolling and heat-treating. Finally, the plate is trimmed and aged at a desired temperature to develop its final properties.

Plate that is slated to become sheet or foil is trimmed after leaving the breakdown mill and sent through a continuous mill to further reduce thickness. Sheet thicknesses are then coiled.

To continue its reducing process, the coiled sheet is heated in a furnace to soften it for cold rolling. Cold rolling is the last step for some sheet, but other types, known as heat-treatable, are subjected to further elevated temperature processing, which increases the metal's strength.

Products and Applications

Plate is used in heavy-duty applications in the aerospace, machinery, and transportation markets.

Aluminum plate, machined to shape, forms the skins of jumbo jets and spacecraft fuel tanks. It is used for storage tanks and containers in many industries, and because aluminum is actually stronger at supercold temperatures, it is especially useful in holding cryogenic (very low temperature) materials.

Plate provides structural sections for rail cars and large ships, and armor protection for military vehicles and the trucks that carry the payroll.

Sheet, the most widely used form of aluminum, is found in all of the aluminum industry’s major markets.

In packaging, sheet is used for cans and closures. In transportation, it provides panels for automobile bodies and for tractor trailer vehicles. Sheet is used in home appliances and cookware. In building and construction, it forms siding and gutters, down-sprouts and roofing, and awnings and carports.

License plates and light bulb bases, pleasure boats and printing plates, highway signs and high flying planes are also all made of sheet.

Sheet can be color anodized to black or gold, red or blue, or hundreds of other colors. It can be etched to a "matte" finish or polished to a sparkling brightness and it can be textured to resemble wood or painted for lasting beauty.

{See also Specialized Aluminum Products for Tool and Mold Applications}[see also Aluminum In Irrigation Systems](see also Aluminum Boats){see also Marine Market Support}[see also Visual Quality Characteristics][see also Aluminum Applications in the Rail Industry]

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