Implementing an ultrasonic inspection system to find surface and internal defects in hot, moving steel using EMATs

Laser-EMAT (ElectroMagnetic Acoustic Transducer) ultrasonics is a suitable technique for on-line surface and internal defect detection in a steel mill. The system is intended to automatically inspect steel, at temperatures in excess of 700C, as it moves through the steel manufacturing process. It is one of the few ultrasonic systems that could ever be used in the harsh operating environment of a steel mill due to its non-contact nature.

In the laboratory and pilot development stages, the equipment can be optimised and designed to work under these harsh conditions. Before the technology can be used on hot, moving product in the steel plant, it is necessary to conduct experiments on moving steel at ambient temperatures, so that system optimisation is performed under more practical conditions. As such, the design of an automated trolley inspection system for inspecting a 1.6 m-long 110 mm-square steel billet at room temperature will be discussed. The laser-EMAT system was later used to find a surface defect in the steel, as it moved at 800C on a pilot scale rolling mill. B-scan data will be presented highlighting the presence of a surface defect on the steel moved both under laboratory and industrial conditions.