The development of a laser-EMAT system suitable for on-line inspection in the continuous casting plant : innovation report

Baillie, Iain
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During the continuous casting process, both surface and internal defects can arise in the as-cast steel semi products, causing problems for downstream processes and customers(l). These problems could be minimised if the steel could be inspected on-line, during the manufacturing process, whereby a feedback control system could be developed to alert operators should any defects arise and modifications need to be made to the process. The main benefit of on-line inspection is reducing operating costs. Additionally, the material flow through the mills and to the customer could be streamlined and optimised to ensure that defective or out of tolerance material is not sent through additional, expensive, value added processes(2,3). The problem is that steel in the caster is at temperatures in excess of 800°C and the environment is so harsh that most inspection technologies will not work under these conditions.\ud \ud A review of the literature was conducted to assess technologies that could be applied to inspect the surface and internal quality of hot, moving steel within the harsh environment of a continuous caster(4). This review enabled a non-contact ultrasonic technique to be selected, as this was suitable for the hostile environment and could find both internal and surface defects at the same time(4). A further literature study was undertaken which showed that a Laser-EMAT (ElectroMagnetic Acoustic Transducer) system could be suitable for the application(5). This technology uses a high energy, pulsed laser beam to generate ultrasound in the steel and noncontact EMATs to detect the ultrasonic signals. As this technology was not available off-the shelf, significant research needed to be conducted and ultrasonic experiments to find defects at room temperature and hot, moving steel were carried out(6).\ud \ud The innovations and main results from important trials conducted as part of this project are included in this Innovation Report. Detailed research and development work, undertaken as part of this project can be found in the 'Steps towards an automated prototype system for inspecting hot, moving steel' portfolio submission(6). The main achievement for this project is the creation of a prototype Laser-EMA T system that could find defects in moving steel, in excess of 800°C.

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