“You can’t get to 54.5 mpg with powertrain improvements alone; you can’t sell enough battery-electric vehicles or plug-ins to get the fleet all the way to 54.5 mpg—you must have weight reduction to make up that gap,” stressed Dr. Blake Zuidema, Director of Automotive Product Applications, ArcelorMittal Global R&D, during his presentation at the recent Great Designs in Steel (GDIS) seminar in Livonia, MI.
The steel supplier recently conducted a comprehensive study based on modeling used by the U.S. EPA and NHTSA (National Highway Traffic Safety Administration) to assess fuel-economy-enhancing technologies and to set the new 2012-2025 standards. The purpose of ArcelorMittal’s study was to evaluate the various lightweighting materials’ abilities to help OEM fleets meet the 2025 target.
The results look “very encouraging for steel,” said Zuidema, adding that it’s not just about meeting 54.5 mpg—it’s about getting there at the lowest cost and the lowest carbon footprint. AEI Associate Editor Ryan Gehm spoke with Zuidema following his GDIS presentation.
Under what scenarios can steel help to meet 54.5 mpg?
Perhaps the most difficult case is all weight reduction coming from the body-in-white (BIW), with no help from any of the other components. Under these circumstances, if we are able to get to the level of powertrain efficiency improvements forecast by the EPA, steel gets you to 54.5 mpg. It provides adequate weight reduction to close that gap… In a scenario where powertrain technologies fall way short of the EPA predictions, not even aluminum or carbon fiber will get you to 54.5 mpg. So there’s a whole continuum; what we found is unless you have a very narrow range of totally unlikely conditions come together, steel still can get you to 54.5 mpg. And if you look at cost-effectiveness, nothing comes close to steel in terms of the value of improving fuel economy. In most cases, the cost difference [between steel vs. aluminum or carbon fiber] was approaching or exceeding $1000 per vehicle. [Zuidema cited industry claims for lightweighting material over-cost: $0.30/lb of weight saved with advanced high-strength steel (AHSS), $2.71/lb saved with aluminum, and $4.87/lb saved with carbon fiber.] But any 2025 fuel-economy strategy must include lightweighting.
What future steel technologies are going to help with this push?
Third-generation steels [which are under development and expected to be ferritic or multiphased steels with enhanced strength and formability] provide additional weight reduction in nonstiffness-limited components. When we did our S-in motion study [in 2010], we started with today’s grades, and then we told the designers, ‘Throw away the portfolio. You tell me what properties you need to make parts lighter.’ What they found is about 20-30% of the parts were still not stiffness-limited even at 1500 MPa, so by going to 1800, 1900, 2000 MPa, we can get additional weight reduction in these areas.
S-in motion showed that as you go from today’s grades to the grades that we’re working on for tomorrow, there’s at least another 5% weight reduction. That’s just in the gauge and grade [2-G approach]; if we can geometry-optimize as well [3-G, which considers load-path efficiency in the equation], there are synergies to get even more. These 3-G approaches provide far and away the greatest opportunity for weight reduction. So with design optimization and with emerging AHSS grades, I’m pretty confident we can get at least a 25% BIW weight reduction [relative to a 2009 baseline]. [Zuidema acknowledged claims that aluminum can achieve a 40% weight reduction with 2025 technologies, and carbon-fiber solutions a 50% reduction.]
(Go to http://www.sae.org/mags/aei/9299 to read more about the S-in motion project.)
What’s your view of the multimaterial vehicle?
With the information that I have based on publicly available sources, it is not cost-effective to go to a multimaterials vehicle. I’ve looked at many multimaterial vehicle strategies, and in every case they met 54.5 [mpg] but they increased the cost relative to an all-steel bodied vehicle. In no case did a multimaterial solution end up with a lower cost than the all-steel solution. As soon as you go to these other materials, you increase the cost and more importantly you increase the carbon footprint.
Now, in other nonbody areas, absolutely [there will be other lightweight materials]. Interior trims, seats—we’re going to need weight reduction wherever we can get it. To me the multimaterial solution is, we have a steel body, steel closures, and the other parts as necessary get that additional weight reduction [from aluminum, carbon fiber, etc.]
What is the time frame for implementing technologies to meet 2025 regulations?
If a vehicle launch is today, it’s getting refreshed in about five years. When a vehicle launches in 2021, that vehicle will still be built by the OEM in 2025—it’s going to count toward their 54.5 mpg. Now back up: they’re probably designing 2021 vehicles right now in the advanced-vehicle stage, but at least three years before start of production we have design freeze—all of the materials and all of the manufacturing strategies are locked in place. So by 2018, all of the materials decisions for vehicles launched in 2021 will be made. That’s why the timing is so critical; there are less than two vehicle cycles between now and when we have to produce 54.5-mpg vehicles.
Is this time crunch understood by OEMs and others?
I have been discussing this message with both the OEM and steel communities for about the past 18 months, and I have seen in perhaps the last couple of months a huge increase in the sense of urgency, both on the steel [development] side as well as on the OEM side. Steel makers have to realize that this is a challenge; it won’t be easy for the OEM community to achieve these targets, and we must make sure that we have every available grade and solution ready to go by 2018, or else they will design vehicles with [other lightweight] materials that get them to their targets. I think everybody now understands that time is ticking away; we need to move quickly.