Page 42 - MetalForming April 2020

Third-Gen. AHSS Arrives in Automotive
Starting with the 2020 model year, the Chevrolet Bolt EV (electric vehicle) will offer an EPA-estimated 259 miles of range on a full battery charge, a 21-mile increase over pre- vious model years.
classes for suppliers to the auto indus- try,” Catterall says, noting that AISI also provides such training. “This training discusses not only materials, but prop- er approaches to stamping AHSS, and how to deal with springback and other stamping issues.”
These classes and related videos also can be found online at www.a- sp.org/training.
EVs Drive OEM R&D
The trend of electric vehicles (EVs) also drives steel and automotive R&D, and signals big changes all through the automotive supply chain.
“We’re seeing many OEMs working on dedicated EV architectures and autonomous vehicles, shifting much of their time and resources to these efforts,” Catterall says. “In fact, current ICE (internal combustion engine)-vehi- cle architectures likely have longer life- times as OEMs concentrate on devel- oping EVs. Though EV development is proceeding, expect ICE vehicles to be around for a few more decades, and you’ll still see a lot of GDIS presenta- tions focused on both EV and tradi- tional vehicles.”
Surveys show vehicle-range anxiety as the biggest concern for end-user customers, driving efforts to employ more powerful battery systems. The biggest architectural challenge in EV development, according to Catterall: packaging battery packs.
“Most OEMs have elected to place these packs in the floor structure, and these packs will need protection from impacts,” he says, “with ultra-high- strength steels serving as the protective material. Underbody architecture must be modified to accommodate and pro- tect the battery packs. Overall, we envi- sion a lot of EV architectures executed in steel due to cost-effectiveness. Use of steel frees budget to pay for other systems that will be required in EVs, such as the battery packs. And, if the industry moves toward autonomy, vehicles will require many more sen- sors, adding weight and needing pro- tection. Again, as steel offers a cost- effective solution for the vehicle
their use for an entire door-side ring. But I’m sure that the industry will work on that.”
Even within the energy-intensive hot stamping process, efforts seek to minimize process costs. It remains to be seen where the efforts will lead.
“Will induction heating of blanks bring down costs?” asks Catterall. “OEMs, Tier Ones and equipment sup- pliers are working on all sides of the hot stamping equation—on how to best cool the dies, trim parts, etc.—and with more and more part providers employ- ing the process, more competition enters, and that will drive behavior.”
Tackling Welding, Joining and Tooling
Development of new AHSS grades, while offering a potential alternative to hot stamping, introduces challenges related to joining mixed materials. Alu- minum welding represents a known challenge, as does the joining of alu- minum and steel, and of other dissim- ilar materials.
“There’s a trend toward mixed-mate- rial solutions in automotive design and build,” Catterall says, describing the increased use of dissimilar materials in vehicle bodies. “That brings the chal- lenge of joining them, including the
joining of various steel grades to each other. We have so many different steel grades used in automotive now—from mild steels all the way to 1800-MPa press hardenable steel (PHS), or poten- tially 2000-MPa PHS—that we’ve sort of created our own mixed-material solutions.”
This introduces the need to modify weld schedules when joining lower- strength materials to higher-strength grades, for example.
“A/SP development projects explore the most efficient ways to weld some of these materials,” offers Catterall. “Spot welding remains the most cost- effective and flexible way to weld pan- els together, and you’ll see the occa- sional introduction of laser welding. But spot welding may be augmented with structural adhesive to increase strength or stiffness.”
Other third-generation AHSS chal- lenges revolve around tooling. Toward that end, A/SP’s Stamping Tooling Opti- mization team, including auto OEMs, steel suppliers, tier stampers and tool- ing shops, conducts research to devel- op optimum standards for tools needed to form AHSS.
“This team helps identify the correct die materials and coatings, as well as die construction, and holds training
40 MetalForming/April 2020
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