Speaker
Description
Laser ultrasound is a non-contact method that enables continuous monitoring of elastic properties in steel samples during thermal processing. Compared with conventional metallographic techniques, it offers substantially higher sample throughput and therefore faster evaluation of relevant process parameters. In this work, we present an approach for in situ estimation of the recrystallization state during recrystallization of cold-rolled steel samples.
The experiments were carried out using an inductive heating thermal simulator whose chamber was adapted for laser-ultrasonic generation and detection through optical windows. An excitation laser locally heats the sample surface, thereby generating ultrasonic waves, while a second laser, integrated into an interferometric detection system, captures the resulting resonances. These signals enable the determination of elastic parameters, which serve as input for subsequent modeling. The measurements were performed on rolled sheet steel samples with a diameter of 62 mm. The method allows elastic property changes to be tracked continuously throughout the thermal cycle. In addition, line shaped excitation of the laser ultrasound makes it possible to measure changes in elastic anisotropy, providing sensitivity to the evolution of crystallographic texture during heat treatment.
The experimental results were compared with simulations and models based on EBSD data. This combination of in situ measurement and microstructure-based modeling enables a deeper understanding of the relationship between recrystallization, texture evolution, and elastic response. The results demonstrate that laser ultrasound is a promising tool for real-time monitoring of thermally induced microstructural changes in steel.
Due to its non-contact operation, high measurement speed, and applicability under industrially relevant conditions, the method also shows strong potential for future inline implementation in thermal processing lines.