� TECHNOLOGY �
Revolutionizing the steel industry: How laser ultrasonics can assist the green steel transition
The steel industry is on the brink of a transformative shift towards greener, more sustainable practices. One promising innovation in this journey is the introduction of a new laser ultrasonic( LUS) based grain size gauge. This cutting-edge technology developed by the Swedish metals research institute Swerim offers unprecedented insights into the microstructure of steel, paving the way for more efficient and environmentally friendly production methods.
Understanding the Basics: What is Laser Ultrasonics?
Laser ultrasonics is a noncontact measurement technique that uses lasers to generate and detect ultrasonic waves in materials. In simple terms, it involves firing a short laser pulse at the surface of a material to create ultrasonic waves, which then travel through the material. Another laser then detects the response of these waves, allowing scientists to analyze the material’ s properties and microstructure. A schematic illustration of the ultrasonic measurement principle is given in Figure 1 below. reflection using another laser. This technique, developed in the 1980s and 1990s, has been commercially employed in the metal industry since the early 2000s for monitoring wall thickness during the production of seamless steel tubes.
The Game-Changer: LUS- Based Grain Size Gauge
The new LUS-based grain size gauge represents a significant leap forward in steel production technology. Installed in the hot strip mill at Borlänge, Sweden, this system is the first permanent setup to monitor the microstructure of steel during hot rolling. The gauge is positioned after the last stand and before the run-out table, ensuring it captures critical data during the production process.
One of the key features of this gauge is its ability to measure
The process begins with a short-pulsed laser, known as a Q-switched laser, which generates the ultrasound by creating a plasma on the material’ s surface. This plasma causes a thermal expansion that generates an ultrasonic shockwave. The response of the ultrasonic wave is then measured by analyzing the Doppler shift of the surface
Figure 1 Schematic illustration of how laser ultrasound works. The pulsed green laser generates the ultrasound, and the response is then measured with the red detection laser.
12 Green Steel World | Issue 17 | April 2025