Taken into use in the 1990s, the X2000 trains have offered comfort, safety and high-speed transport for millions of passengers in Sweden. The current upgrade process seeks to extend the trains’ lifespan by decades, with the original stainless steel train frames continuing in use.
In the late 1980s, the Swedish state railway company SJ wanted to create a fast and comfortable transport option to air travel between major cities like Stockholm, Gothenburg, Copenhagen and Oslo. The high-speed X2000 trains – altogether 40 trainsets – were introduced into service between 1990 and 1998. The trains had a special design including a tilting system and radial bogies, which allowed for high speeds of 125 miles per hour on curved tracks, without compromising passenger comfort and safety.
The vehicles were manufactured by ABB, who, after careful consideration and lifetime assessments, chose stainless steel, made in Outokumpu’s Avesta mill in Sweden, as the main material for the train frames.
The X2 upgrade project, currently underway, seeks to extend the trains’ service life by another 20 years by replacing some of the technical components including the propulsion and auxiliary systems, upgrading the doors and fully renewing the interior. The original stainless steel train frames, however, will stay in service into the 2020s and 2030s, saving both money and natural resources. Over time, investing in quality stainless steel has proven to be the right, cost-effective choice.
Speed and strength through the decades
Initially, ABB decided on stainless steel as the main material for the train frames based on a thorough lifecycle analysis. It was calculated that in the long-term stainless steel was a lighter, safer and cheaper option than aluminum or carbon steel. For instance, the savings in maintenance costs per railcar over a period of 30 years were estimated at 100,000 Swedish kronor (ca. USD 17,500 today), and the weight reduction per car was about 20% compared to carbon steel.
The lighter build also means that less energy is needed to propel the train, which translates into considerable energy savings over time. All in all, stainless steel met both the speed and safety demands set for the X2000 fleet while also giving the trains a beautiful streamlined exterior.
“The frame is designed with a high level of bending stiffness which reduces vibrations and increases travel comfort. In addition, the stainless steel grade has excellent impact resistance in a collision situation, improving passenger safety,” explains Carl Jallinder-Björkman, Technical Project Manager from SJ, who is in charge of the technical part of the X2 upgrade project.
Combined with lower maintenance costs and long service life, stainless steel – an austenitic grade, which today is called Forta 304/4301 in cold-worked condition for enhanced strength – was the optimal choice for the fast and firm train frames. “This stainless steel application, though designed in the late 1980s, has a truly advanced car body which shows influences from aircraft design by utilizing a load-bearing shell structure,” says Outokumpu technical market development expert Claes Tigerstrand. “The frames have a lightweight build which still provides the stiffness and strength needed for high-speed trains.”
Cost-effective and sustainable solution
Today, two decades and millions of miles later, the promises of durability and long service life are proven true. “The lifetime assessment and inspections determined that the frames were largely intact. No damages or notable corrosion have occurred to them,” Jallinder says.
The upgrade project, first announced in 2014, promises to return the entire X2000 fleet back to service with improved reliability and comfort by 2018. In addition, the upgrade will significantly reduce the trains’ energy consumption.
According to Jallinder, being able to upgrade the fleet and reuse the original train frames is a major gain for SJ, proving that stainless steel is a choice that pays for itself in the long-term. “For one, upgrading is about four times cheaper than buying new trains. In addition, this decision supports SJ’s long-term corporate social responsibility strategy; the environment is of major importance for us, and upgrading the X2 fleet instead of having to invest in new vehicles has a significant positive impact on our environmental footprint”, Jallinder explains.
“This application highlights how crucial it is to apply lifecycle thinking when choosing materials, something Outokumpu has always encouraged customers to do,” adds Tigerstrand. “Looking at both costs and environmental impacts, choosing the right, sustainable stainless steel really pays off.”