Electromagnetic techniques for imaging the cross-section distribution of molten steel flow in the continuous casting nozzle

Control of molten steel delivery through the pouring nozzle is critical to ensure an optimum laminar flow pattern in continuous casting, which influences the surface quality, cleanliness, and hence the value of the cast product. A nonintrusive and nonhazardous visualization technique, which uses rugged and noninvasive sensors, would be highly desirable in such harsh industrial production environments. This paper presents an electromagnetic approach for tomographically visualizing the molten steel distribution within a submerged entry nozzle (SEN). The tomographic system consists of an eight-coil sensor array, data acquisition unit, associated conditioning circuitry, and a PC computer, which have been purposely designed and constructed for hot trials. The paper starts with an overview of electromagnetic imaging techniques. The construction of the sensor array and associated electronics are then discussed, followed by sensitivity map analysis and a description of the applied image reconstruction algorithm. Image results, as reconstructed from cold sample measurements and hot pilot plant trials, are also presented. Despite a low frame acquisition rate (1.35 s per frame), the images generated from the prototype system are capable of providing an adequate representation of the changes of real molten steel flow profiles within the SEN. The paper demonstrates that the application of electromagnetic tomographic technique to this problem shows significant promise for future industrial processes.