Ultrasound as key to fossil-free steel production

Through new methods for optimizing the microstructure of fossil-free steel, one of the sub-projects within the FINAST research program contributes to accelerating the steel industry's transition to a carbon-neutral future by studying alternatives to heat treatment and thermomechanical treatment of steel.

The study treats steel with ultrasonic waves that interact with the metal's internal structure with the aim of improving the efficiency of current heat treatment and metalworking techniques. Today, the technology is successfully used in processes such as wire drawing and extrusion to change the flow properties of metals. In the sub-project where Patricio is a PhD student, acoustic tempering and possibly hardening using ultrasonic treatment will initially be studied and how well the technology can be applied to the fossil-free steels of the future. Ultrasonic processing of metals is based on the efficient absorption of the mechanical energy of sound waves at room temperature. This contrasts with conventional heat treatments, where most of the energy is used to heat the whole material to the desired temperature, and only part of the energy consumed is used to activate mechanisms that induce a change in the material. The aim is to improve and streamline traditional processes using ultrasonic treatment while reducing energy consumption.

High demand for innovative solutions

"Although the interaction between metals and ultrasonic waves has been known for many years, the recent demand for innovative solutions to reduce CO2 emissions in the steel industry gives us an opportunity to go back to basics and rethink how metals are processed," says Patricio Piantanida, PhD student in materials engineering.

Other properties can also be affected by ultrasonic treatment. As a first study in the sub-project, steel from SSAB has been surface treated with ultrasound and Patricio is currently working on analyzing and interpreting the results of the treatment. Some of the samples will be sent to Swerim in Kista to investigate how the material's resistance to hydrogen embrittlement is affected by the ultrasonic treatment.

"The collaboration with Swerim takes place within the FINAST project. We learn from each other and we encourage the PhD students to collaborate. In the study, we examine SSAB's steel and the hydrogen testing is carried out at Swerim, both of which contribute with their expertise in the areas," says Marta-Lena Antti, Professor of Materials Engineering.

Great potential

The potential of ultrasound to improve production processes while reducing energy consumption makes the technology interesting in the future development of the metal industry and through the project in FINAST, Patricio will study the extent to which the fossil-free steels can be treated.

"We are currently making investments in the lab for further studies, a highly interesting area to study is the heat treatment performed after cold processing, whether we could replace or streamline that step with the help of ultrasonic treatment," concludes Pia Åkerfeldt, Assistant Professor of Materials Engineering.