Castings

Casting is a simple, inexpensive, and versatile way of forming aluminum—so it is not surprising that it was also the first method used.

Such items as the baby rattle for the French’s emperor’s son, the cap atop the Washington Monument, and the tea kettle were all produced by aluminum casting.

The Production Process

Today, casting is the most widely used method of forming aluminum. Technical advances, of course, have been made, but the principle remains the same: molten aluminum is poured into a mold to duplicate a desired pattern.

The three most important methods are die casting, permanent mold casting, and sand casting.

Die casting, in which molten metal is forced into a steel die, or mold, under pressure is normally used for high-volume production. Accurate parts, requiring a minimum of machinery, can be produced via this method.

Permanent mold casting involves molds and cores of steel or other metal. Molten aluminum is generally poured into the mold, although a vacuum is sometimes applied.

Permanent mold castings can be made stronger than either die or sand castings. Semi-permanent mold casting, which uses expendable cores of sand or other material, is used when permanent cores would be impossible to remove from the finished part.

The most versatile method is sand casting. Virtually any pattern can be pressed into a fine sand mixture to form a mold into which the aluminum is poured. This is a slow process, but it is usually more economical for small quantities, intricate designs, or when a very large casting is needed.

Casting Products

The automotive industry is the largest market for aluminum castings, and cast products make up more than half of the aluminum used in cars. Cast aluminum transmission housings and pistons have been commonly used in cars and trucks throughout the world for many years. Still many other engine parts are also cast from aluminum, and the applications grow as automakers seek new ways to save weight and gain fuel efficiency and performance.

Cast aluminum is also widely used in other forms of transportation, including aircraft and marine engines and other structures.

Parts of small appliances, hand tools, lawnmowers, and other machinery use thousands of different aluminum castings. But the cast product most often seen by consumers is cookware—the aluminum product that was the first made available for everyday use.