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 historical 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 casting.
The Production Process
Today, casting continues to be the most widely used method of forming. Technical advances, of course, have been made, but the principl
e 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.
Permanent mold casting involves molds and cores of steel or other metal. Molten aluminum is generally poured into the mold, although 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 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 housing and pistons have been virtually universal in cars and trucks throughout the world for years. Many other engine parts are cast 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 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 product that marked the beginning of low-cost everyday aluminum use.
