Strain-induced precipitation HSLA steels

Purpose and goal

We have investigated the possibilities of measuring recrystallization and strain-induced precipitation by doing realistic in-situ experiments at synchrotron radiation facilities mimicking the finishing mill process. It is of interest to understand whether recrystallization is retarded by solute drag or by particle pinning. We have identified combined scattering (SAXS, WAXS) measurements as a viable approach. A roadmap towards in-situ synchrotron experiments has been drafted and beam time has been applied for at the Swedish beamline at PETRA-III.

Expected results and effects

The pre-study has resulted in four deliverables: a background technology document from SSAB, a survey of experimental capabilities, a roadmap towards realistic in-situ measurements and a beam time proposal. We have limited the investigations to X-ray tomography and scattering techniques (SAXS, WAXS), which are suited for studies of the micro-scale grain structure and the nano-sized precipitates, respectively, covering the full interesting size regime. These techniques can in principle be applied for in-situ experiments involving mechanical loading and high temperatures.

Planned approach and implementation

The pre-study was performed during slightly more than three months. The parties in the project were SSAB, Uppsala Synchrotronix (USync) and Lund University (LU). The activities comprised investigations regarding ex-situ and in-situ measurements at synchrotron beamlines, discussions in tele conferences, and a workshop in Lund including a visit at MAX IV. Outside the project plan, Stephen Hall did preparatory tomography measurements in his laboratory at LU. A sample was also tested at PETRA-III and a strong signal was received which is very positive for future measurements.