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Twinning-Induced Plasticity (TWIP) steel, which contains very high concentrations of manganese, offers outstanding mechanical properties combined with impressive strength. It is also very ductile, which means that it stretches under stress.
This has caught the eye of the automotive industry, which looks for new materials capable of delivering lightweight, flexible and safe parts for vehicles of the future. European component suppliers – as well as steel producers looking for new markets – also stand to benefit from the commercialisation of this high-performance steel.
“Our main objective in the TWIP4EU project was to really show that TWIP steels are viable materials in the production of automobile components,” says TWIP4EU project coordinator Alexander Butz from the Fraunhofer Institute for Mechanics of Materials in Germany. “To achieve this, we developed, tested and have now made commercially available, software simulation models that can be used to accurately describe the forming behavior of TWIP steels.” This, he adds, will increase the quality of the numerical simulation and help to speed up part production.
The flexibility of TWIP steel makes it very attractive for automotive applications because it means more complex shapes can be easily produced for car parts. Its ductility also provides energy absorption levels at more than twice that of conventional high strength steels, offering extra protection in the event of a crash. In addition, the strength of the material allows for a reduction in sheet thickness used to make the components, contributing to a more efficient use of resources and lightweight potential.
“Several feasibility studies were performed within this project that showed the potential of this material for lightweight and high-strength car components,” says Butz. Since parts like a backrest made of TWIP-steel weigh less compared to standard metal materials, there is also a positive impact on the environment.
Precision and strength
To be commercially attractive, however, TWIP steel needs to be cost efficient. This means developing highly efficient manufacturing processes on an industrial scale. A key step towards this is being able to quantify material performance for the automotive sector.
“In order to introduce TWIP steels for large-scale applications at industrial level, we realised that we first needed to demonstrate we could describe the forming behavior of the material at industrially required precision,” says Butz.
TWIP4EU was divided into three main parts. To begin with, the project carried out extensive experimental analyses of TWIP steel material. This data was used to develop simulation models to describe the forming behavior of TWIP-steels, and then translated into software code. Finally, the precision and accuracy of the developed software model were determined by comparing the application with data obtained from different forming experiments.
Ready for business
The TWIP4EU simulation model has since been implemented into two commercially available software packages. During the project, the software was used to successfully design and produce TWIP steel components, which demonstrated its excellent formability properties.
“Also, the numerical results which were obtained from simulation corresponded with our experimental findings,” Butz says. “This shows that the software modelling is accurate for industrial demands.”
Upscaling of the production process to fit the needs of an industrial-sized steel plant is currently ongoing, and Butz is confident that large scale production of TWIP-steel material will begin shortly. “As soon as this starts, we expect to see an increase in demand for TWIP-steel,” he adds.
This project received financing from the EU’s Research Fund for Coal and Steel.