- By Matthew
- In Metal Processing, Rolling Mill
- Tags Alloys
Aluminum and Aluminum Alloys
Aluminum has many advantages. The first advantage is that it is light weight or has a low specific gravity. Steel weighs 0.28 pounds per cubic inch. Aluminum weighs one third of steel. If you take the weight of steel and divide by three, you will have the approximate weight of aluminum. Of course, this has a large advantage in the aircraft industry and has made inroads in the automobile industry, such as lightweight aluminum wheels, which reduces the kinetic energy required to accelerate or decelerate. Many other innovations in aluminum have been made in the automotive and truck industries. For example, many trailers and railroad cars are made of aluminum. By reducing the weight of any vehicle, the energy for acceleration and deceleration is reduced making more load possible.
Aluminum has other great characteristics. Cost should be considered because if steel costs .40 cents/pounds and aluminum being one third the weight of steel, you could pay three times more per pound for aluminum and receive the same volume. However, most aluminum is not as strong as steel. Depending upon its alloy, it has less yield and tensile strength than carbon alloys. However, by adding chrome and other alloys to aluminum, aluminum can approach the strength of steel. This is very common on aircraft landing gears.
As with carbon steels, aluminum has many alloys. Pure aluminum is very soft with a low yield strength, which has many advantages, such as deep drawing when making beverage cans, bearing material, foils, etc. Aluminum forgings can be very strong, approaching the strength of many steels, as used in the structural parts of a vehicle.
Aluminum has other possibilities. It can be used for electrical components, including bus bars because it has a high degree of electrical conductivity. Certain aluminum is corrosion resistant and used in the chemical industry. It is common in cooking utensils because it has a high conductivity of heat transfer. A lot of food packaging is done with aluminum foil.
Aluminum can be extruded so it is used for all type of shapes, such an angle, flat bar, etc. It is certainly used in the furniture industry because of its light weight. Aluminum can be polished, anodized or coated, so it holds a reflective surface for a long period of time. This is common with concentrated solar collectors.
Since aluminum carries a high price per pound, it is collected and recycled. Most aluminum cans are re-melted and made again into aluminum strip. The aluminum strip can be painted so you have a painted sign or light weight building material. In Africa, there are many buildings made from painted aluminum strip that was melted from recycled aluminum beverage cans, which are ideal near a salt water coast.
Aluminum foil from a rolling mill is used to make all types of capacitors. Aluminum foil is used in the tobacco and the food industries. Foil is made from hot rolled strip up to .250” thick and is rolled to .008” to .0002” thick by up to 72” wide, but generally 48” to 60” wide. Aluminum can corrode, however, but with the low cost of anodizing, corrosion can be minimized. This type of rolling mill sometimes operates at over 3,000 FPM.
Scrap aluminum is easily melted and made into aluminum foil, strip, or plate. All kinds of aluminum alloys are made to increase strength or to make soft for substantial cold working without heat treating. Aluminum alloys can be soft and cladded to steel as used in connecting rods and main automobile bearings instead of using Babbitt, a lead alloy which is a pollution concern. Many aircraft bearings are made from aluminum alloys, including high strength aluminum alloys such as aluminum bronze. There are many paints that can used to paint aluminum any color, which is useful in light weight appliances, as well as automobiles and buildings.