Steel sustainability
Under pressure to reduce costs and fuel consumption, the transportation industry is increasingly facing the need to build lighter, more fuel-efficient vehicles. This focus will have a positive effect on the environment. Advanced high-strength steel (AHSS) is already contributing to environmental sustainability across the product development lifecycle, from material production to use and, finally, end-of-life recycling.
Just ask Jan-Olof Sperle, professor and specialist in lightweight design. Sperle is conducting research on how AHSS makes lighter products and is helping develop methods to easily evaluate the effects of reduced environmental impact and costs.
“Using high-strength steel is an important part of the chain which helps to reduce fuel costs and CO₂ emissions. It’s a fact that higher strength steel is a more sustainable solution than conventional steel,” he says.
Using high-strength steel instead of conventional steel in vehicles reduces the weight of the upgraded parts of the vehicle by as much as 25 to 40 percent. In turn, this means less energy is needed to power the vehicle, leading to reduced fuel consumption and lower carbon dioxide emissions, while increasing the payload on load-carrying vehicles.
“Manufacturers of cranes and other weight-sensitive equipment were the ones who first saw the potential of high-strength steel,” says Sperle. “Today we find these steel grades in many other contexts, but the whole community would benefit if the use would increase even more.”
If one million tonnes of advanced high-strength steel were used today for the European road vehicle fleet, instead of 1.3 million tonnes of conventional steel, savings of 8,000 kt in carbon dioxide and 28,500 GWh of energy resources would be achieved; over 90 percent of these savings are related to use of the vehicle. In essence, this means that every million tonnes of advanced high-strength steel used in the European vehicle fleet would reduce CO₂ emissions by eight million tonnes.
So, with numbers like these why aren’t more companies using advanced high-strength steel?
Sperle thinks it might be due to a lack of experience, conservatism and old standards. “At the same time, we see a lot happening right now,” he says. “The intensifying debate about the environment and the climate clearly highlight reduced weight as a method to achieve quick results. And that is exactly what this research leads to in its extension.”
Based on a large number of cases, Sperle shows that doubling the yield strength leads to about a 30 percent weight loss for the upgraded areas of the structure.
The increased proportion of high-strength steel also means that fewer natural resources are needed for each vehicle, which reduces emissions from steel production. And the savings in fuel help reduce emissions from driving the vehicle.
Today, information is available about materials as well as design and production techniques regarding advanced high-strength steels. Sperle’s research project adds an environmental dimension.
“To achieve the greatest possible environmental effect, it is important than knowledge and techniques and materials are easy to access,” says Sperle. “This means, for example, that the research findings should also be reported as simplified relationships between the properties of steel, the weight of the structure, the operating conditions and the environment.”
Can increased strength translate into lower weight? Does high-strength steel provide improved performance, including higher loading capacity, crashworthiness, impact resistance, wear resistance and corrosion resistance?
“Our studies show positive results for high-strength steel in almost all contexts,” says Sperle.
For vehicles in weight-critical applications, a weight reduction can directly translate into increased load capacity and a corresponding reduction in environmental impact. Energy consumption decreases the most when high-strength steels are used in subway trains, trucks in construction work, and cars with custom drivetrains. Fuel savings are greatest when there are many starts and stops, heavy acceleration, hilly terrain and low to moderate speeds.
“Saving weight in the production of your vehicle is really worth it,” concludes Sperle.
(Parts of this research were conducted in close cooperation with the steel industry, which already uses some of the environmental and cost benefit analyses in manuals for designing and dimensioning high-strength steels.)