Automotive Engineering - September 2024 - 29

tarSTEEL
gets EV
structures,
battery boxes
The industry fires back
at aluminum's growing
'gigacasting' threat.
by Lindsay Brooke
GDIS 2024 keynoter Brad Davey, executive VP of corporate business optimization at ArcelorMittal.
T
he steel and aluminum industries are waging a new materials
war that could determine which of the long-time competitors
dominates EV structures in the next design cycle. Feeling the
heat from new aluminum applications, steel companies are
aggressively moving to defend their reign as the material of choice in
vehicle body structures. They also aim to conquer the EV battery enclosures
market, currently dominated by aluminum extrusions. (See
AE March 2023 feature: https://www.nxtbook.com/smg/sae/23AE03/
index.php#/p/CVR2.) Steel executives are bullish on their new technologies
and their approaches to winning on both fronts.
" Today, many automakers are talking about high-pressure die-cast
aluminum, especially for BEVs, " Brad Davey, executive VP at steel
giant ArcelorMittal said. Speaking with SAE Media following his keynote
address at the recent 2024 Great Designs in Steel (GDIS) conference
in Novi, Michigan, Davey acknowledged that giant HPDC aluminum
'gigacastings lend themselves to 'skateboard' EV platforms
due to their potential to consolidate parts and simplify manufacturing.
The end benefit, he said, " is capital-expense assembly line savings, "
particularly for EV companies.
" If you can reduce floor space and the number of welding robots in
assembly, by using one large casting, it can be an attractive solution
- compared with traditional processes, that is, " he said.
Pioneered by Tesla on the Model Y, gigacastings are designed to
ultimately form a battery-electric vehicle's entire underbody in a single
aluminum component. The Model Y uses two castings, front and
rear, connected by a steel/aluminum battery box. See AE June 2020
feature: https://www.nxtbook.com/nxtbooks/sae/20AUTP06/index.
php#/p/Intro). The potential benefits have sparked industry-wide
interest, especially in tooling suppliers like IDRA, LK Group, Buhler,
and Yizumi. In late 2023, GM acquired Livonia, Michigan-based
Tooling & Equipment International (TEI), a leader in foundry mold
AUTOMOTIVE ENGINEERING
technology. GM engineers used TEI's expertise to prototype
and validate the large underbody castings for
the Cadillac Celestiq due later this year.
Despite recent reports that Tesla scaled back its effort
to produce a low-cost Model 2 using an industryfirst
single underbody casting, steelmakers are also
concerned about Chinese OEMs using aluminum gigacasting
to help drive radical new EV architectures. S&P
Global has reported development in China of enormous
12,000- to 16,000-metric-ton HPDC machines.
Gigacasting downsides
Not so fast, the steel stalwarts say. ArcelorMittal's
Davey highlighted gigacasting's downsides. " The part
costs are higher. If you're not offsetting the part costs
with manufacturing savings, you're going to end up
with a higher cost design or no cost improvement, "
he said. " There are many issues on yields, defects
related to high tooling cost and trying to extend tooling
life, and also cracking [of the castings]. He also
noted casting's crash-energy absorption characteristics
and questioned OEMs' ability to refresh/change
exterior body styling as quickly and efficiently as on
traditional structures.
" Typically, in the past, aluminum solutions have
been lower weight, but these are not compared to the
optimum steel solution, " Davey said. Optimizing mold
flow through the large die-cast parts has, in many
cases, required increased wall thickness and larger/
heavier castings overall, he said. He also claimed that
September 2024 29
MATERIALS FEATURE
LINDSAY BROOKE

https://www.nxtbook.com/smg/sae/23AE03/index.php#/p/CVR2 https://www.nxtbook.com/smg/sae/23AE03/index.php#/p/CVR2 https://www.nxtbook.com/smg/sae/23AE03/index.php#/p/Intro https://www.nxtbook.com/smg/sae/23AE03/index.php#/p/Intro

Automotive Engineering - September 2024

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