Steel E-Motive

Steel E-Motive represents a fully autonomous ride sharing vehicle concept showcasing the strength and durability of steel with a critical focus on sustainability for reaching net zero emissions targets. The results are comfortable, safe and affordable body structures that support automakers in the continued development of Mobility as a Service (MaaS) ride sharing models.

The program highlights two virtual concepts designed for 2030 to 2035 deployment: SEM1, a four-passenger urban transport, and SEM2, a six-passenger extra-urban commuter, both designed for Level 5 autonomy with no steering wheel or pedal box.  Both vehicles have the potential for more than an 85% total lifecycle CO₂ emissions reduction by 2035, based on a comparison with a reference 2022 battery electric vehicle (BEV).  A rigorous Life Cycle Assessment (LCA)  approach was applied throughout the development of the Steel E-Motive concept. Both of these facets are highlighted in Figure 1.

Figure 1: Key Contributors to Life Cycle Emissions Accounting Include Decarbonized Steel Production, Projected Battery and Electrical Grid Performance Improvements, and Operational Contributions of Autonomous MaaS. 

Vehicle life cycle performance can vary considerably depending on where the vehicle is manufactured and operated. To account for this, life cycle performance of the Steel E-Motive concept was calculated for Europe, US, China, Japan and India regions.

Steel E-Motive concepts were developed for mixed traffic mode operation –  thus safety was paramount. The SEM1 concept vehicle represents one of the world’s first autonomous vehicle engineered to meet global high speed crash regulations that can achieve the IIHS “Good” rating. The battery packaging approach is 37% lighter and 27% lower in cost than average reference battery case structures, and applicable for current BEVs in development. This innovation includes an air gap between the battery modules and removable bottom cover, providing additional security from road debris, and the opportunity for battery inspection and local repair, vs. battery box replacement.

Detailed simulations showed both concepts are manufacturable using global manufacturing and supply infrastructure at costs that can support profitable margins, both for the vehicle manufacturer and mobility service providers.  Annual volumes of more than 250,000 vehicles for SEM1 and 90,000 units for SEM2 were contemplated in the projections.

Using the newest steel grades and fabrication processes, Steel E-Motive’s portfolio enables tailoring vehicle properties that achieve significant comfort, safety, and cost advantages with seven key innovations:

• A one-box open body B-pillarless structure provides a wider door aperture for easy ingress/egress, disabilities access and facilitates delivery services.
• A scissor door design integrating side impact protection directly into the door frame creates a compact section for better passenger visibility and improved passenger access while eliminating the body side outer for mass and cost savings.
• The Extended Passenger Protection Zone created with Advanced High Strength Steels provides excellent intrusion protection for rear-facing front passengers.
• The Short Front Crash Zone structure enabled by the use of PHS, MS and laser welded blanks meets the most stringent global crash requirements.
• The Small Offset Crash Glance Beam minimizes cabin intrusion and lowers crash pulse by creating a “glance-off” the barrier – preserving door ring and battery in 64 kph small overlap rigid barrier simulations.
• Hex beam energy absorbers in the rocker minimize side crash intrusion and achieves superior battery protection.
• An industry-first Battery Carrier Frame eliminates the conventional battery case, utilizing the existing floor as the top cover, and features an AHSS triple-skinned bottom cover that seals the battery and provides protection from road debris and jacking errors.

The Steel E-Motive program meets these requirements through extensive use of Advanced High-Strength Steels which offer favorable combinations of strength, ductility, toughness, and fatigue properties.

Different AHSS grade have unique properties which can be beneficial to different parts of a vehicle structure. Dual Phase and Transformation-Induced Plasticity steels are used in vehicle crash zones for their high energy absorption. Intrusion prevention is accomplished through the use of Martensitic and Press Hardened Steels.

The average tensile strength of the body structure is more than 1250 MPa, facilitating a lightweight structurally safe vehicle designed and fabricated to minimize the lifecycle carbon footprint.

The figures below highlight the types and deployment strategy of the steels used in the Steel E-Motive body-in-white. The full spectrum of grades in the portfolio are shown on our Defining Steels page. Of the grades shown in the full portfolio, 18 grades of steel, at 12 different gauges, were used in the primary Bill of Materials (BOM) for SEM1, for an average part sheet steel thickness of 1.2mm.

Figure 2: Steel E-Motive SEM1 BIW design and distribution of AHSS

Figure 3: Steel E-Motive BIW AHSS grade allocation

Figure 4: Steel E-Motive BIW AHSS grade distribution

FutureSteelVehicle

Started in 2008, the FutureSteelVehicle (FSV) program built on more than a decade of work finding ways to decrease vehicle mass, reduce cost and meet comprehensive crash safety standards, all in pursuit of a smaller environmental footprint. FSV validated wide ranging research into the practical use of AHSS, innovative design and manufacturing technologies, and proposed specific examples for electrified vehicles (Figure 1).  FSV used Life Cycle Analysis (LCA) to select the steels and manufacturing techniques that result in the lowest total carbon footprint, going beyond accounting only for emissions in the use phase.

Figure 1: FutureSteelVehicle Battery Electric Vehicle Concept ^{W-11, W-12}

FutureSteelVehicle drew from a broad portfolio of steel types and grades, in a range of properties from mild to GigaPascal strength levels, applying a vast array of manufacturing processes. With advanced optimization algorithms, FSV incorporated hundreds of variables in the design process to identify a wide band of solutions. This approach integrated vehicle design, powertrain design and packaging, occupant space, passenger ingress/egress, driver sight angles, NVH, and aerodynamics to achieve a body structure that works in harmony with all vehicle requirements related to more stringent emissions and fuel efficiency standards while meeting safety (crash) standards and affordability.

The FSV project included structural variants for battery electric (BEV), plug-in hybrids (PHEV-20 and PHEV-40) and fuel cell (FCEV) powertrains, these same design attributes can be applied to conventional ICE-powered vehicles as well. Figure 2 highlights the FSV body materials breakdown.

Figure 2: Future Steel Vehicle Body Materials Usage

Lower Weight

Extensive use of a broad portfolio of AHSS grades, coupled with engineering design optimization, enabled a robust body structure that is feasible to produce and achieves 5-star crash performance against all global crash standards, while also exceeding mass reduction targets. A lower weight, mass-efficient body creates opportunities for downsizing sub-systems, including the powertrain, and promotes reductions in overall vehicle mass. As an example, the body structure mass achievement for the FSV BEV variant is 177 kg ^W-39, including the battery tray – a component unique to a Battery Electric Vehicle. This compares quite favorably with the 2010 VW Polo, at 231 kg, which was recognized as Car of the Year in Europe because of its mass-efficient design but carries a lighter ICE gasoline powertrain. Table 1 highlights some of the benchmarking comparisons.

Lower Cost

Steel is the most cost-competitive material for car bodies. It is economical to fabricate into components and sub-systems and to assemble into the total body-structure assembly. The resulting cost estimate of $1,115 to manufacture and assemble the complete FSV body validated this proposition and represents no cost penalty compared to vehicles at that time.

Lowest Total Lifetime Emissions

FutureSteelVehicle demonstrated the importance of Life Cycle Assessment as an integral element of a vehicle design process. In combination with optimizing the design for mass, cost, and functionality, FSV integrated into all analyses an accounting for its complete environmental footprint as measured in CO₂e. It more appropriately comprehends the entire lifetime carbon footprint of the vehicle, not simply the use phase. This includes the entire fuel production cycle (well to pump), the fuel usage cycle (pump to wheels), the production of raw materials, as well as disposal/recycling.

FSV demonstrated that the coupling of a lightweight, AHSS body structure with a battery-electric powertrain results in a 50 to 70 percent reduction in total life cycle emissions, compared to equivalently sized vehicles with conventional gasoline ICEs ^W-12. Furthermore, based on the new steels’ light weighting capabilities, steel is the only material to realize emission reductions in all life cycle phases. Table 2 summarizes total vehicle carbon footprint and emissions performance by life cycle phase.

Safety

The FSV design anticipated increasingly stringent crash safety standards over the decade following its release and was designed to meet European and U.S. 5-Star crash safety performance requirements over that time ^W-12. Using the latest holistic design and material optimization approaches combined with steel’s unmatched capabilities for design and manufacturing efficiency, the final FSV design comprised optimized, mass-efficient shapes that met or exceeded these global crash safety requirements.

Rationale

Automakers face conflicting constraints when designing new body structures:

• With escalating concerns about human-induced green-house gases, global legislators have passed increasingly stringent vehicle emissions regulations, with even more aggressive targets planned for the coming years. Lighter weight body structures promote reduced vehicle emissions.
• Fuel price increases lead to greater consumer sensitivity to vehicle fuel economy. Lighter weight body structures also promote improved fuel economy.
• One of the easiest ways to reduce vehicle weight is to use thinner metal. To maintain crash performance, this thickness reduction must be accompanied by an increase in the strength of the sheet metal grade.  Since thickness and stiffness are related, decreases in thickness must be accompanied by other methods to increase stiffness: either using a high-modulus material like steel, and/or using design features like darts or beads to lock in the shape.  The chosen grade must be sufficiently formable to successfully incorporate these features.
• Automaker marketing departments highlight spacious interiors. Greater room can be accomplished by making larger vehicles, but the extra weight does not support mass reduction. On the other hand, use of more formable steels is a cost-effective way to increase packaging efficiency.  New vehicle designs with complex geometries are aesthetically pleasing, but are difficult to form and join unless the chosen alloy has the necessary balance between strength and ductility.
• Global crash and safety regulations must be contemplated, especially if one body architecture will be used as the basis for vehicles intended for sale in multiple regions around the world. Increasing sheet metal thickness improves crash performance, so any reduction in thickness must be paired with using high strength grades where the deformation characteristics can be tuned to optimize crash energy management.
• All of these challenges must be addressed with sustainability in mind.

The global steel industry continues to develop new grades of steel defined by ever-increasing strength and ductility, continually reinventing this diverse material to address these challenges faced by automakers.  Advanced High-Strength Steels (AHSS) are characterized by unique microstructures and metallurgical properties that allow OEMs to meet the diverse functional requirements of today’s vehicles.

Worldwide working groups within WorldAutoSteel member companies created the AHSS Application Guidelines to explain how and why AHSS steels are different from traditional higher strength steels in terms of press-forming, fabrication and joining for automotive underbody, structural, and body panel applications. This website provides in-depth current information on a wide range of topics related to successful application of these steels.

Automotive companies around the world have adopted different specification criteria. Steel companies have different production capabilities and commercial availability. As a result, the typical mechanical properties provided on this website simply illustrate the broad range of AHSS grades that may be available worldwide.

In addition, regional test procedures will cause a systematic variation in some properties measured on the same steel sample. One example is total elongation, where both measurement gauge length and gauge width are a function of the standard to which the test is conducted (ASTM, DIN, or JIS, also known as ISO I, II, or III), with these differences impacting the measured value. In addition, property requirements can be defined relative to either the rolling direction or transverse direction. Therefore, communication directly with individual steel companies is imperative to determine grade availability along with specific test procedures, associated parameters, and steel properties.

• About
  • Rationale
    • ULSAB and the Early Steel Consortia
    • FutureSteelVehicle
    • Steel E-Motive
    • Emissions and Life Cycle Assessment
    • Performance Advantages
    • Current Vehicle Examples