STEEL AND FUEL ECONOMY

Sometimes I think we all take steel for granted. We see it everywhere. Steel is an intrinsic part of our lives, including our cars. We make steel from iron, an abundant element, so the supply is virtually unlimited. Today's average vehicle has over 60 percent steel in its makeup.

Yet I think people assume steel is the same today as it has always been. But let me tell you point blank that that today's steels for cars and trucks are not at all like the steels we used 40 years ago. Back in the 1960s, formability, shape and styling were king. Our industry responded with deep drawing steels to make the wonderful shapes of the classic cars of that era.

But as time rolled on, the challenges for auto materials got tougher. The 1970s brought the first oil crisis, and from that our first drive was birthed to reduce vehicle size, weight, and fuel consumption. CAFE was born.

Steel responded by creating a new class of high strength steels, including HSLA (high-strength low alloy). This was, ironically, the same metallurgy used to create the high-strength, high toughness line pipe steels used for the Alaska pipeline.

HSLA was a very affordable way to reduce mass. Mass savings with this steel was essentially free – the reduction in the amount of steel purchased covered the costs of the new grades. In Figure 1 you can see how HSLA more than doubled the available strength of automotive steels. Automotive steels were being reinvented
for the needs of the time.

In the 1980s warranty issues cried out for more corrosion resistant steels. Galvanized sheet steels of all sorts were introduced, including electrogalvanized, hot dip galvanized, and galvannealed varieties. The steel industry invested heavily in the new coating lines to make these product and car companies invested in new welding capability to deliver the higher currents required for good welds. The result was new 5-, 7-, and 10-year long-term warrantees, better value for consumers, and evidence again that steel can adapt to the needs of the time.

Ever since the 1990s, the U.S. has studied ways to reduce vehicle mass as an enabler for more fuel efficient vehicles. Al Gore's PNGV (Partnership for a New Generation of Vehicles) research conducted through the US-DOE did not include steel, so the global steel industry funded $33 million of research on ULSAB (ultra-light steel auto bodies), which promoted advanced ultra-light steel vehicle concepts to show that new steels, especially advanced high-strength steels, can achieve over 25 percent mass reduction and meet all vehicle requirements. Since 1990, vehicles have gotten safer and are held to increasingly stricter standards for crashworthiness, as Figure 2 shows.

In fact, the vehicle structure – which used to be designed for stiffness – is now controlled primarily by strength – perfect for our new advanced high-strength steels (AHSS). In 2007, a new CAFE law was passed and NHTSA is now working out the details of the rulemaking that will take effect beginning in 2011. Clearly, reducing the mass of vehicles will be an important contributor to achieving these higher fuel economy targets. We have proven that the new high-strength steels can be a major factor in mass reduction.

With the use of today's AHSS, steel can achieve at least 25 percent mass reduction (see Figure 3). Furthermore, with new third generation steels now under research, we expect to achieve over 35 percent in structural mass. Before I close, please consider that fuel economy isn't the only factor when it comes to the environment. The effect of the choices we make, for example in materials, can influence how much GHG we place in the atmosphere as well.

As you can see from Figure 4, steel has a relatively low greenhouse gas (GHG) emissions level for production, much lower in fact than the lower density materials often considered for mass reduction programs. This means that during its production stage, a low density material vehicle will load the environment with significantly more GHG emissions than steel.

In Figure 5, using a University of California steel and life cycle assessment (LCA) comparison model, we show an advanced high strength steel vehicle (in blue) and an aluminium vehicle (in yellow). In this case, because the aluminium vehicle releases a significantly higher level of GHG emissions during the material and production phase, it never falls below the emissions for the steel vehicle during its lifetime. This chart tells us that putting too much emphasis on the use phase of life can lead to the unintended consequences of higher GHG emission.

Ronald Krupitzer is the vice president for automotive applications at the American Iron and Steel Institute, 2000 Town Center, Suite 320, Southfield , MI 48075, 248-945-4761, www.autosteel.org, [email protected].