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S-in motion® Plug-in Hybrid Electric Vehicles (PHEV)

Tighter emission regulations have led OEMs to explore different vehicle powertrain options to dramatically reduce weight while remaining competitive. Many OEMs and automotive analysts believe that hybrid powertrains will offer the best cost-benefit compromise for OEMs while meeting consumer demand for unlimited range in the medium term.

ArcelorMittal has undertaken a study to determine how S-in motion® solutions can be applied to a plug-in hybrid electric vehicle (PHEV). The S-in motion® PHEV project identified the weight saving potential of advanced high strength steel (AHSS) on PHEV vehicle architecture.

An innovative body-in-white design and process changes can help to achieve weight savings at neutral cost, despite the heavier powertrain. The study also identified the challenges of converting a vehicle powered by an internal combustion engine (ICE) vehicle to a PHEV.

PHEV vehicle showing ICE and electric powertrains

Hybrid powertrains present unique challenges for car designers. As well as accommodating a conventional internal combustion engine (ICE), the vehicle also has to carry a battery and electric motor.

This leads to

  • Almost 200 kilograms to the weight of a typical C-segment vehicle
  • Requires additional reinforcement in the body-in-white (BIW) structure

Weight saving thanks to increased use of AHSS

The S-in motion® PHEV study showed that it was possible to decrease the BIW weight by increasing the use of AHSS (including hot stamped press hardened steels) to 57%, up from 37% in the baseline vehicle.

  • The number of LWBs was more than doubled to 18 parts (up from 8).
  • Hot stamping was utilised in 31% of the BIW (up from 6%). LWBs are an effective way to reduce weight while still maintaining performance by putting exactly the right steel in the right place.
  • Press hardened steels (PHS) are utilised for 24 parts of the PHEV BIW, mainly Usibor® and Ductibor® . PHS offer high mechanical resistance for complex geometries without springback.

Meeting crash tests regulations

A significant challenge was ensuring that the optimised PHEV could meet the updated crash test scenarios. The pole crash test is one of the most difficult to satisfy as the PHEV has additional weight in the front (electric motor) and the back (battery pack). The solution was to make a hot stamped cross member from Usibor® 1500. This offers outstanding protection against side impacts.


The final results of the S-in motion® PHEV study showed that ArcelorMittal’s advanced high strength steels (AHSS) and solutions have the potential to cut 55 kg from the BIW, leaving it just 9 kg heavier than the lightest ICE BIW.

S-in motion® again proves that AHSS have the potential to dramatically reduce vehicle weight while improving safety, and at neutral cost to the carmaker.