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Sustainability Helps Shape Promising Future for Automotive Steel

by Bernard Swanson Jr, Senior Director - Product Development and Engineering


 

In the battle of public perception regarding the environmental sustainability of steel versus aluminum in the auto industry, aluminum proponents have long advanced a talking point that is compelling in its simplicity. It holds that since aluminum is lighter, vehicles with a higher ratio of aluminum to steel are likely to be more fuel efficient.

The point is logical as far as it goes. Its problem is that it doesn’t go nearly far enough. And what it misses makes a huge difference in the pursuit of sustainability, especially in light of recent technology advances in both the steel and automotive industries.

Innovations in steel design have greatly narrowed the gap of aluminum’s weight advantage, while steel continues to enjoy decided advantages in recyclability and manufacturing properties. Moreover, improved automotive battery technology is making steel a more attractive — and ultimately more sustainable — choice for supporting the growth of battery electric vehicles.

Light Weighting

Let’s look deeper at each of these factors, starting with weight. It’s important to remember that light weighting is not simply a matter of using a material with the lowest mass. In the auto industry, it requires optimizing the balance between weight and strength. Because steel is stronger than aluminum, auto bodies made of aluminum must be thicker to achieve the strength and safety of steel — and aluminum’s weight advantage is diminished.

With the introduction of advanced high strength steel (AHSS) more than a decade ago, the weight differential shrank even further. AHSS steels allow automakers to the achieve the strength of general steel grades using less material, hence achieving lower weights.

Now, further metallurgical advances are creating additional opportunities for automakers take advantage of steel’s combination of strength, formability and lower cost versus aluminum. U. S. Steel’s Generation 3 steel, 980 XG3™, can be stamped into even the most complex parts, which supports automakers’ desire for design flexibility, while offering the high-strength profile that enables the use of less material to lower weight.

Recyclability

Formability is a key sustainability advantage in more ways than one. In addition to supporting a wider range of car designs, it enables parts and panels to be stamped with less waste. Also consider that the smaller amount of steel waste generated in the stamping process can also be recycled more efficiently than aluminum, which requires costly and time-consuming sorting by grade. Scrap steel on the other hand, can be comingled.

Overall, recyclability strongly favors steel, which is the world’s most-recycled material. Steel is infinitely recyclable, and industry studies have determined that about 80 to 90 percent of the steel ever produced is still in use in some form. The automotive steel recycling story is even more compelling. Nearly 100 percent of vehicles that are taken out of service in the United States are recycled, which results in 15 million tons of steel scrap being recycled every year. That’s the equivalent of 11.6 million automobiles.

Cost Advantage for BEVs

Next, let’s consider the most impactful sustainability trend in the automotive industry today — the introduction and adoption of battery electric vehicles (BEVs). Conventional wisdom would say that light weighting is especially important in this market because a lighter vehicle can travel farther per battery charge. However, recent advances in battery technology have substantially improved battery efficiency and BEV range. Given that the weight difference between aluminum and steel bodies already has a relatively small impact on average range, introduction of new batteries will make the difference even less significant.

What is important to the sustainability story is consumers’ adoption of BEVs, and that is largely driven by price. Because steel costs substantially less than aluminum, automakers can offer consumers a lower sticker price, which makes their vehicles affordable to larger segment of the population. Indeed, many automakers who initially used aluminum construction for their electric vehicles are now switching to steel.

That’s not the end of the story, either. Ultimately, steel is the more sustainable choice when the entire lifecycle of the material is considered. One recent study compared lifecycle greenhouse gas emissions for an electric vehicle made from steel versus one made from aluminum. The study found a significant energy savings with steel, driven largely by a lower energy demand in the metal manufacturing process. The bottom line, according to the study, was that automakers could produce 17 percent more BEVs using AHSS with the same lifecycle energy demand of BEVs made with aluminum.

In a society increasingly focused on reducing the environmental impacts of greenhouse gas emissions, steel is the more sustainable choice in the automotive market. Understanding lifecycle energy analyses and the corollary benefits of steel might not make for a simple story, but it certainly is the most powerful one.

 


About the author

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Bernie Swanson is Senior Director of Product Development and Engineering.