Steel eliminates weight gap with aluminum car bodies

The latest in a continuing series of research studies strongly suggests that steel auto body structures in the near future can be as lightweight as today’s aluminium bodies, while meeting all crash performance standards and at comparable cost of current steel structures. The studies also address critical manufacturing challenges, showing that car makers can form and fabricate sophisticated steel designs, thus accelerating implementation of this technology into production vehicles.

Adding to a weight reduction of 35% in its initial FutureSteelVehicle design, the steel industry’s most recent studies boost the mass savings to 39%, compared to a baseline steel body structure carrying an internal combustion engine, adjusted for a battery-electric powertrain and year 2020 regulatory requirements. The optimised FSV body would weigh just 176.8 kilogram’s, putting steel on par with today’s  aluminium production designs. An industry database of current production vehicles (A2mac1) shows this light-weight, Advanced High-Strength Steel (AHSS) body structures, designed to carry heavier electrified powertrains, fall in line with the lightest internal-combustion-engine aluminium vehicles, and are on par with other concepts featuring multi-material solutions.

The study results show that by incorporating FSV technology, car makers can avoid pursuing more costly alternatives involving competing materials and multi-material designs to achieve their goals.

“Our latest light-weighting  projects show the continuing potential of steel and demonstrate  how car makers can take advantage of steel’s design flexibility and use Advanced High-Strength Steels (AHSS) to meet their difficult challenges for improving fuel economy and reducing green-house gas emissions,” said Cees ten Broek, Director, World Auto Steel, the automotive group of the World Steel Association.

The two most recent studies,  called 'FSV Final Gauge Optimisation' and 'FSV Near-Term Front Longitudinal Rail Shape' streamlined the FSV design and devised alternative geometry (for the front rails), respectively. The former led to an additional mass reduction of 11.6 kg, compared to the initial FSV design, bringing the total weight savings to 39%. The latter validates two different, but comparable, front rail designs, expanding the range of solutions available to car makers in the near term.

The first study following announcement of  the  FSV  in  May  2011  was  3B  (Draw Bead, Blank Geometry and Binder Pressure) Forming and Crash Optimisation.  It resulted from continuing development of the  Multi-Disciplinary Optimisation (MDO) Process that enabled the “Nature’s Way” design used in FSV and solved the remaining forming issues  presented  by  the  FSV’s  unique Front Rail structure. Through this design optimisation work, the very efficient, light-weight Front Rail design is now a viable option for future production vehicles.  Further, with the addition of the 3B Forming Process, the optimisation software now fully comprises solutions to AHSS formability issues.

Intensive use of AHSS, as the FSV demonstrates, also contributes to lower total green-house gas emissions over the entire vehicle life cycle, compared to higher cost, more energy-intensive low-density materials. 

Through this advantage in lower total life cycle emissions, steel use is consistent with a growing movement toward regulations that comprehend all sources of emissions, not only those from the vehicle-use phase.

The FSV programme developed optimised AHSS body structures for four proposed 2015-2020 model-year vehicles: battery electric (BEV) and plug-in hybrid electric (PHEV) A-/ B-Class vehicles; and PHEV and fuel cell (FCEV) C-/D-Class vehiOff White X Nike Design