What Heavy-Duty Truck Manufacturers Know About Aluminum

While aluminum vs. steel is getting more contentious in the world of light-duty trucks, when it comes to creating structures, the heavy-duty truck people know something important about strength and mass.

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Although the recent Chevy ads pitting the steel in the box of its Silverado against the aluminum in the F-150 might make it seem as though aluminum is some exotic stranger when it comes to truck application, a stranger that one might be best advised to shy away from, JD Rutt, vice president of business development at Sapa Extrusion (sapagroup.com/en/na/profiles), makes an interesting point about aluminum and trucks that is well known by some, but perhaps not thought about by others: 

When it comes to heavy-duty trucks—such as Class 8 tractors and trailers—aluminum has been a material of choice for a number of years. While light-duty vehicle engineers are chasing lighter-weight materials for the purpose of helping meet impending CAFE requirements, Rutt says that fleet owners, for years, have been working to optimize the weight of their vehicles for purposes of “freight efficiency,” not for a third party’s rules. That is, the lighter the structure—both tractor and trailer—then the greater the load. So Sapa, he says, has been providing the vehicle manufacturers with extruded components to build the bodies-in-white, as well as a variety of components, including such things as top and bottom rails and I-beam support structures, for the trailers.

“They want to be able to carry the maximum load—so they don’t want the weight in their trailer materials,” Rutt says.

“The durability of aluminum use in these applications is well-documented,” he adds.

Rutt says that Sapa specializes in extrusions that are used in a variety of vehicle body-in-white and chassis applications, and not just for vehicles that are generally considered “aluminum-intensive,” although they, of course, are in that space as well. (For example, the company supplies extrusions to Ford for the F-150.)

One of the bigger application areas is for bumper beams due to the compression characteristics of the material; many of the bumper beam applications are made with 6082 alloy, which provides the formability and ductility that provides the shapes that are required for the applications as well as the crash energy management needed for the application.

(The aluminum alloys that are often used in extruded applications have a tensile strength from 150 to 300 MPa.)

They’re making side sills, A-pillars, B-pillars and a variety of other body and closure components. There are roof rails and sill plates. Seat structures and sunroof components. Control arms. “A lot of control arms,” Rutt says. Motor mounts. Even blocks for ABS systems.

Although in the post-2015 Ford F-150 world one might imagine that there would have been a considerable rush toward the deployment of aluminum in all manner of applications, according to Rutt, the growth hasn’t been as extreme as could be imagined, and he acknowledges that one thing that they are seeing is an increase in the number of programs that are based on mixed-material applications, not just one type of material—although he does acknowledge that there is a growing number of vehicles that are truly aluminum-intensive, vehicles that are coming from OEMs located in various parts of the world.

He also acknowledges that there is increased competition coming from the steel industry, where developments in areas like ultrahigh-strength materials are being launched. That said, he goes on to point out that Sapa has a cadre of metallurgists that are dedicated to not only tailor materials for specific OEM applications, but who also are working on creating alloys that are stronger so that various components can be made with thinner wall sections, thereby making what is already a comparatively light-weight material even lighter. (The density of aluminum is 2.7 g/cm3, or about a third that of steel.)

Another growing area where Sapa is finding growth is in electric vehicle batteries. Here, Rutt says, extrusions are used to form a frame around the battery pack, the level of complexity and sophistication being predicated on the cooling method for the batteries.

As the industry moves toward the 2025 CAFÉ regulations, Rutt believes that aluminum is going to make further inroads in vehicle structures (as well as hang-on panels, though that’s not the space Sapa is in). Speaking of aluminum, he says, “It is versatile. Available. The technology is there. The automakers are educating themselves—what are the best alloys, the best processing methods? So as I look forward to the 2019, 2020 models, I see a substantial amount of aluminum content out there.”