Aluminum wheels are typically manufactured using one of three currently popular methods. Aluminum wheels are divided into cast wheels, forged wheels, and flowform wheels. Before we discuss each of the three methods, let’s understand what aluminum and aluminum alloys are.
Aluminum
To achieve low rotating weight, manufacturers use aluminum to produce rims. Aluminum is a chemical element extracted from mines, and then, after physical and chemical processing (e.g., a bath at temperatures over 900°C), it is created into a metal used in many industries.
Aluminum alloys
Various aluminum alloys are produced for various industries, depending on the desired properties. An aluminum alloy is aluminum alloyed with other additional metals (or non-metals). Copper, silicon, magnesium, manganese, and zinc are the most common components found in aluminum alloys. Various aluminum alloys are used to produce aluminum rims, affecting, among other things, the metal’s strength, corrosion resistance, and plasticity. They are classified according to their chemical composition and described in technical standards (related to production technology) – PN-EN 573-3+A1:2022-11 (formerly PN-EN 573-3:2019-12). This standard defines 17 grades of aluminum, each with varying degrees of purity. Purity ranges from 99.00 to 99.99%.
Cast wheels
These are among the most popular types of rims, available commercially in sizes starting from 13″. The most common alloy used in the production of cast rims is the A356 aluminum alloy. One of the main alloys used in cast rims is the A356.0 alloy, in which the main alloying elements are silicon with copper and/or magnesium. Cast alloys are not suitable for plastic processing, such as forgings or semi-finished products for forging, or extruded products (e.g., profiles) or rolled products (sheets, plates). During production, the aluminum alloy is melted and poured into the rim mold (using a vacuum). It is then cooled and subjected to final mechanical processing and painting. The rim is cast in a die and a punch.
Due to the alloy’s chemical composition and the high temperatures it is exposed to (even melting) the material is less resistant to damage than forged rims made of EN AW-6XXX alloys. The less complex production process and weaker production material translate into a higher final product price. Cast rims are the cheapest type of rim after steel rims.
Flowform wheels
The second popular type of rims are flowform wheels. This is a transitional design between cast and forged rims. Like cast rims, they are made of A356.0 aluminum, but the production process is slightly different.
The entire rim is cast similarly to cast rims, but the flowform rim’s drum is shorter at the time of casting. After the cast rim is removed from the mold, it undergoes the next stage: plastic drum forming. The rim drum is then heat-treated (at a temperature lower than melting to preserve the metal’s structure) and rolled to the desired length. This process results in a rim drum that is more durable than a cast rim.
Forged wheels
Forged wheels are the strongest and lightest type of aluminum wheels. They are made from durable aluminum alloys, primarily 6-series. Magnesium and silicon are the primary additives in 6-series alloys. They are characterized by high strength, good ductility, and very good corrosion resistance. 6061 aluminum (designated EN AW-6061 / EN AW-Al Mg1SiCu) is the material we use to produce Turismo forged wheels. It is also used in the construction of heavy structures, such as railway wagons, truck frames, and in ship and bridge construction.
6061 aluminum alloy can also be anodized—an electrochemical process that creates a layer of aluminum oxide on the surface. This treatment significantly increases strength and corrosion resistance. Anodizing allows it to be colored using organic dyes (conversion of aluminum oxides into boehmite). This process allows for a wide range of rim colors.
The production process for a forged wheel is significantly more complex than that of a cast or flowform wheel. The process begins with a forging—a block of aluminum created in a steel mill through thermal and plastic processing. The hot aluminum is rolled using high-pressure hydraulic presses. This gives the aluminum additional strength. The forging is the basic prefabricated part in the creation- of a forged aluminum wheel. The finished forging then moves to a CNC machine, where the process of milling the wheel from the aluminum block begins. The milled wheel undergoes inspection and quality control, before undergoing further processing.
The high quality of forged rims results from the use of durable alloys, CNC machining and, very often, individual finishes.
