Online Lecture by Prof. Ronald Schnitzer

Microstructural changes due to increased use of scrap in steel production
Ronald Schnitzer, Lukas Hatzenbichler, Nikolaus Kostwein, Oleksandr Glushko

Head of Chair of Physical Metallurgy
Christian Doppler Laboratory for Knowledge-based Design of Advanced Steels,
Department of Materials Science, Technical University of Leoben, Austria

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Title:
Microstructural changes due to increased use of scrap in steel production
Ronald Schnitzer, Lukas Hatzenbichler, Nikolaus Kostwein, Oleksandr Glushko.

Abstract:
The transformation of the production routes in the steel industry from blast furnaces to electric arc furnaces enables an increased use of scrap and thus significantly reduced CO2 emissions in the manufacturing process. This change will inevitably increase the amount of undesirable tramp and trace elements in steel products. Knowing the exact amount and type of elements is crucial to determine their influence on the microstructure and mechanical properties.

In the course of the presented work, phase transformations and scale-bridging microstructure characterization, including high-resolution methods such as atom probe tomography and in situ high-energy X-ray diffraction, were performed on alloys with different contents of tramp and trace elements. In addition, machine learning methods were used to support the evaluation of microstructures.

The results show that impurity elements not only shift the phase fields for longer periods of time, but also lower the phase transformation temperatures. In addition, it has been observed that impurity elements inhibit the growth of the former austenitic grains by accumulating at the grain boundaries at high temperatures. There was also a decrease in notched impact strength with increasing amounts of Sn, Sb and Cu. Using atom probe tomography, nm-sized Cu clusters along the grain boundaries as well as a significant enrichment of Sn and Sb at grain boundaries could be detected.

This session was chaired by prof. Erik Offerman (Delft University of Technology, the Netherlands.)