Page 47 - MetalForming Magazine February 2023 - Metal Forming for the Automotive Industry

About the Cover
Lucid Motors recently has invested in aluminum hot-forming technology from AP&T to hot-form several unique, lightweight stamped components from high-strength aluminum, for this new Lucid Air luxury vehi- cle, which was named 2022 Motor Trend Car of the Year.
The hot-forming project dates to 2015 when Lucid sought technology to manufac- ture crash-critical stampings such as door rings, B-pillar stiffenings and battery-pack protection components. According to Eric Bach, Lucid’s senior vice president of product and chief engineer, “AP&T presented a prom- ising new technology. The potential benefits were significant, because hot forming enabled the manufacturing of complex part geome- tries with high-strength aluminum.”
Lucid supplier fischer group commis- sioned the new hot-forming line in December 2021 at its plant in Achern, Germany. Per AP&T, the scalability of the process enables its use even for lower volumes.
A conventional aluminum hot-forming process for hardening the material is to heat it to its solution heat treatment temperature, followed by forming and cooling in the die. Artificial aging typically then is used to obtain the desired mechanical properties—time- consuming, as well as increasing the mate- rial’s hardness, which can crate challenges in downstream joining operations.
To alleviate these concerns, AP&T’s process, company officials say, employs an optimized aging sequence to reduce cycle time, by including a “pre-aging” process (5 to 30 min.) after forming and quenching the part, to prepare the material for a final hard- ening/paint-baking process that occurs after assembly of the car body.
Fischer reportedly expects to soon begin manufacturing high-strength aluminum parts using the process near the Lucid assembly facility in Casa Grande, AZ, where Lucid has said it plans to ramp up production to as many as 400,000 vehicles/yr.
• 6000 series—Bake hardened and used for outer panels and structural cold-formed parts.
• 7000 series—"Where we approach the limits for cold forming,” White shares, “and start to look at hot form- ing for high strength and more com- plex shapes with the best material uti- lization.”
In addition, with aluminum metal formers gain some forming options that they might not have with some higher-strength steels, White explains. “Roll forming is a good example of this,” he says, “where we can roll form as easily or more so than steel. We also can extrude profiles, and even combine some parts with structural castings to develop near-net-shape parts, reducing overall part and joint count.”
Formability Guidelines
White and his team at Alumobility are hard at work developing formability guidelines for aluminum. “We’ll start with the basics,” he says. “For example, where a steel part calls for a 2t bend radius, a similar aluminum part requires a 3t minimum radius. The guidelines also will establish safe limits for thinning—18 to 20 percent thin- ning, for example, compared to 26 to 28 percent on a steel part.”
The challenges with aluminum occur more with drawing, where metal formers fight oil canning or local stiff- ness issues. Here, says White, die designs must include additional swages to get more stretch from the material, for example.
“Once we understand the rules of the road,” White stresses, “we pretty much can replicate any steel part in aluminum. And when moving to hot forming, we can deliver the same radii, or even tighter with aluminum, than with a hot-formed steel parts. We know that hot-formed aluminum can func- tion in the same vehicle package as an AHSS B pillar or door beam. Hot form- ing essentially takes away any differ- ence in formability between steel and aluminum.”
What about springback? “We know that we can predict springback; we
don’t fear it and it’s no different than with AHSS,” White says. “With the needed springback-compensation rules in place—adding features to the part or cutting the die to compen- sate—metal formers can do all of the things with aluminum that they can do with AHSS. And here, simulation often is more important that it is with steel.”
In 2022 Alumobility published—and made available on its website—its Sin- gle-Piece Aluminum Body Side Outer Panel-Design & Process Guidelines, offering up a slew of recommendations for details such as opening radii; die design and development (five opera- tions typically needed—draw, trim, reform, restrike, flange and pierce); draw-bead design; and recommended trim, shear and pierce angles. And, the document describes and illustrates an aluminum-specific tool design to enhance deep-drawability, using upper-die floating inserts for front and rear door apertures in the bodyside outer panel.
What’s Next?
White and Greco tell us that there’s a joining design guidelines document in the works, a project that’s been ongo- ing for the past year. And, the group is developing additional forming guide- lines as well.
“We completed a big joining project last year,” White says, “and used the outputs of this latest OEM project to help us develop the new guidelines. We’ll share that document on our web- site, and we’ll do the same with the forming guidelines, using the results of our body-side development project where we’ve gone through a full simu- lation to show the advantages of alu- minum versus existing production parts.”
This approach by Alumobility has seen increased interest and engage- ment, says White, with further studies coming in 2023 and additional projects confirmed, to demonstrate that a com- bination of lightweighting and efficien- cy can produce more sustainable vehi- cles in the future. MF
44 MetalForming/February 2023
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THE SCALING UP OF AUTOMOTIVE ALUMINUM