Last year, when the Obama administration passed the new corporate fuel economy standards, requiring cars and light trucks to average 54.5 mpg, it was a moment of celebration for everyone concerned about the environment and the rate at which carbon emissions are damaging our climate system.
For carmakers, though, it was more likely a day to reach for the antacid rather than the champagne. All the testing, modeling and forecasting showed that even with all the dramatic improvement being made to powertrains, including electric cars, hybrids, plug-ins, diesels, etc. showed that given the rates of adoption and the distribution of vehicle sizes, there was no way that the companies could reach the average fleet economy goal based on powertrain modifications alone. To achieve these new levels of fuel economy would require making cars lighter. But reducing the weight enough to make a difference without compromising vehicle safety would likely require the use of exotic materials such as carbon fiber composites, which could add significantly to the cost of the vehicles.
Fortunately, advances in high strength steel, have led to substantially improved strength which can allow for thinner, lighter parts, without compromising safety – at a reasonable cost.
This was all explained to me by Blake Zuidema, Director of Global R&D, Automotive Product Applications for ArcelorMittal, the world’s largest steel and mining company, and leader in automotive sheet steel technology.
Triple Pundit: I’m surprised to hear this. After all, people have been making steel for a long time.
Blake Zuidema: Ten years ago structural steel had a yield strength of 270-350 MPA (mega-pascals). Today’s advanced high strength steels (AHSS) can go as high as 1500 MPa. These new steels have evolved using a combination of new formulations and alloys as well as different processing and treatment techniques. The newest steels are not only stronger, but they also tend to be more formable. This gives steel producers a rich and diverse portfolio of material options that can be custom tailored to meet the requirements of each application. It also represents a change in how steel companies like ArcelorMittal approach our business, transforming ourselves from providers of raw material, to providers of solutions.
3p: So how have you been able to achieve this kind of success with light-weighting?
BZ: It’s really a combination of design and materials. ArcelorMittal has learned that clearly, the key to weight reduction is not just substituting a lighter material or a stronger, thinner gauge material, because those things only take you so far. You must approach this in a holistic design optimization program to get maximum structural efficiency out of the vehicle. Keep in mind most vehicle structure designs were based on the grades of steel and the strengths of steel that were available in the past. Today, with the advent of AHSS, there are things we can do in a clean sheet redesign of the vehicle’s structural load paths, we can get a substantial reduction in vehicle weight. We have made this conversion by first developing and then sharing the expertise in how a specific steel formulation can be developed to meet a given design objective.
3p: What about the use of these other materials like carbon fiber and aluminum; are they not needed?
BZ: The claims of proponents of other materials do have some merit – there are other materials that can also provide the kinds of weight reduction that the industry is looking for. But you have to take a look at which approach can deliver the desired result most cost effectively. We have to be careful that when we improve fuel economy we don’t end up raising prices to the point where they will hurt vehicle sales.
3p: So you must have come up to speed quickly on this.
BZ: Actually no. The first push for weight reduction came back in the 70s with the original oil embargo. Back then we introduced a whole range of high strength alloy steels that enabled us to get a lot of weight out. But then in the 80s and 90s there was a big push for improved safety, which would have added substantially to the weight of vehicle if we hadn’t continued to develop new steels that were both stronger and lighter. Now, with the new fuel economy standards, weight reduction has become more important than ever.
3P: So what kind of weight reductions are we talking about?
BZ: We’ve seen automakers, in the last year or so, come up with new vehicle body designs that are 15 to 18 percent lighter than the designs that came before them. These were all achieved with steel that are available today and are in commercial production, though they might not have been available a few years back.
3P: That’s quite impressive.
BZ: It is, indeed. But that is not taking advantage of all the weight reduction capability that we have developed. If they were to incorporate all these advances, that number would grow to around 25 percent, which would be enough, based on the actual models that EPA uses to calculate the fuel performance of various vehicle models, to meet the 54.5 mpg CAFÉ standard. So, we are confident that steel is a viable solution and a cost-effective way to reduce vehicle weight in order to achieve this very aggressive new fuel economy standard. And something else that people may not know is that pound for pound, steel takes less energy to produce than carbon fiber, aluminum or magnesium.