How a Car Alloy Rim is made?
Higher-end cars typically come with alloy wheels rather than basic steel wheels covered with a hubcap, often called mag wheels because they were originally made from an alloy of magnesium. Today’s alloy wheels are made of an aluminum alloy, which is far more durable and desirable. Aluminum alloy wheels are not only more attractive than standard steel wheels, but they also weigh a fraction of what steel wheels do, requiring less energy to rotate. This contributes to greater fuel efficiency as well as better handling, acceleration, and braking.
Manufacturing aluminum alloy wheels begins with high-grade aluminum alloy containing 97% aluminum. A furnace heats the ingots to 750 degrees Celsius, liquefying the aluminum in about 25 minutes. The molten aluminum then flows directly to a mixer, where argon gas is injected to remove hydrogen, increasing the density and making the aluminum less porous when solidified. Powdered titanium, magnesium, and other metallic elements are added to further strengthen the aluminum. The blend includes flux, a chemical that draws aluminum oxide to the surface, which is skimmed off along with the flux impurities, making the liquid aluminum ready for casting.
The wheel mold is made of high-strength steel and consists of three parts: the upper mold, which forms the inside face of the wheel; the forepart side mold, which forms the wheel’s edge; and the lower mold, which forms the intricate outer face. It takes three to four weeks to produce a mold. Computer simulations check the flow and temperature of the liquid aluminum, which are critical for preventing casting defects. The casting machine fills the mold from the bottom by pressurized injection, reducing the risk of air bubbles that can cause defects. The molten metal flows through a high-temperature-resistant ceramic filter to trap additional aluminum oxide. Once cast, the aluminum takes about seven to ten minutes to solidify, after which the mold automatically opens to release the newly cast wheel. Workers submerge the wheel in lukewarm water for a few minutes to cool it down enough to be handled.
The wheel then undergoes a complex heat treatment process that takes 12 hours. This process involves heating the wheel to strengthen the molecular structure of the metal, followed by quenching in 80-degree water for 30 seconds to lock in the new strength. The wheel is then reheated to 180 degrees for nine hours to further stabilize the metal.
After heat treatment, the wheel edges are rough due to excess metal that needs to be trimmed off. The wheel is mounted on a computer-guided lathe that precision machines the sides to within 0.05 millimeters of the specified measurements. A worker manually trims the more intricate face of the wheel with a blade. Once the shape is finalized, the wheel is tested for airtightness by submerging it in water while pumping air into it. If air bubbles appear, indicating a pinhole in the metal or shrinkage, the wheel fails inspection.
If no air bubbles appear, the wheel proceeds to the automated painting line, receiving a base coat, a coat of color (ranging from classic silver or black to flashier shades), and a clear coat to protect the paint and prevent corrosion. From every batch of approximately 1,500 wheels, the factory randomly selects two or three for performance and wear testing. Finally, workers install a decorative cap that covers the center hub and typically bears the brand’s logo. A final cosmetic inspection ensures that the aluminum alloy wheels look as good as they perform.
