Forged aluminum wheels
Hot forging and cold reeling
Forged aluminum wheels are one piece, which is made from one metal blank by hot forging, followed by hot or cold rotary deformation processing (rolling) and mandatory mechanical processing.
forging technology makes it possible to realize the most diverse design, almost as well as in the alloy wheels. Forging the entire rim of the one piece ensures a higher strength properties and smaller weight as compared with composite constructions, as well as cast aluminum wheels and, of course, with steel wheels.
Figure 1 – Forged aluminium wheels for high performance applications (Source: Alcoa) [1]
Figure 1-1 – Wheel (A6061) for truck forged by Kobe Steel Co [2]
Benefits forgedx aluminum wheels
- Forged wheels are usually at about 25 % lighter alloy wheels.
- While molding and is a cheaper process, alloy wheels show significantly lower mechanical properties, than forged wheels.
- Components forged alloy composed of two or more parts, which are interconnected in different ways. In some composite disks used bolting, in others - welding or adhesives. In any case, the compounds in composite rims act as stress concentrators and place of occurrence of fatigue cracks. Bolting can be a source of vibration to subside or.
- Forged aluminum wheels are superior cast aluminum wheels, especially with respect to impact and fatigue strength. Forged wheels do not break under impact tests, whereas it impact tests are a problem for alloy wheels.
- Increased fatigue strength of forged wheels gives designers the opportunity to further reduce their weight, in the same time, staying on the fatigue strength of no worse than cast wheels.
Figure 2 – Forged wheels offer a variety of design variants (Photos: Otto Fuchs) [1]
Advantages of aluminum forging
1) The forging process makes it possible to fully exploit the properties of the material in relation to:
- mechanical properties;
- viscosity;
- fatigue strength.
2) Forging technology achieves very tight tolerances on the dimensions of the rims. The forged rims are no porosity and shells, which means high reliability.
3) The surface of the forged wheels gives more possibilities for its final finishing.
Aluminum alloys for forging disks
standard alloys, which are used for forged aluminum rims are heat-hardening alloys of the AlMgSi alloying system (6xxx series):
- 6082 in Europe and
- 6061 in North America.
Full designation aluminum alloy 6082 according to the European Standard EN 573-1 looks like this: EN AW-6082 or EN AW-AlSi1MgMn, and alloy 6061 - EN AW-6061 или EN AW-AlSiMgCu. Alloy 6082 - is an analogue of the domestic aluminum alloy AD35, a raft 6061 - alloy AD33 GOST 4784-97.
Wrought aluminum microstructure
Forging stretches the microstructure of the metal along the direction of metal flow (Figure 3) and thus allows the full use of the strength and toughness potential of the alloy.
Figure 3 – Forging aligns the grain structure of aluminium with the shape of the wheel (Source: Alcoa) [1]
Although forged, and alloy wheels must meet the same specifications of the strength characteristics and reliability indicators, forged wheels are more resistant to overloading and incorrect use.
Compared with alloy wheels, forged wheels exhibit a high fatigue endurance due to the absence of porosity and the presence of small, homogeneous microstructure (figure 4). Moreover, dense microstructure deformed literally will reach mirror surface disk after machining of a diamond tool.
Figure 4 – Fatigue life curves of forged AlSi1MgMn -T6 and LPDC AlSi7Mg0.3-T6 (Source: Otto Fuchs) [1]
Manufacture of forged aluminum wheel
Conventional technology for manufacturing of forged aluminum wheel includes a plurality of forging operations, rough machining, heat treatment, finish machining and various intermediate and finishing treatment depending on the construction and design.
Technology company Otto Fuchs chain for the manufacture of lightweight forged wheels, first used back in 1995 year, comprising the steps of, shown in Figure 5.
Figure 5 – Production steps for light weight forged wheel (Source: Otto Fuchs) [1]
Sources:
- European Aluminium Association, 2011
- Forging /Encyclopedia of Aluminum and Its Alloys – Eds. George E. Totten, Murat Tiryakioglu, and Olaf Kessler – 2019
