Evaluation and optimization of electromagnetic stirring (EMS) parameters for continuously cast high carbon billet quality using ultrasonic c-scan imaging

Abstract

In recent years, there has been a tremendous increase in demand of clean steel. Hence more attention has been paid to improving product quality with respect to overall cleanliness level, reliability, and quality of continuously cast steel product. Continuous cast billet has a heterogeneous structure. Depending upon the cooling conditions, a chilled zone is first formed at the region in contact with the mould followed by columnar and then equiaxed zone at the core. Carbon segregation at equiaxed zone may lead to cementite formation at localized regions thereby increasing hardness ultimately causing breakage while wire drawing operation. Hence a large equiaxed zone is desirable, so that segregation per unit area is reduced. Using electromagnetic stirring (EMS) it is possible to achieve effective and reliable stirring of the molten steel in the continuous casting process, which can meet the metallurgical objective of improving the quality and productivity of cast products. By controlling the EMS current and frequency, stirring intensity in the liquid pool can be controlled. Recent studies on optimization of current and frequency of EMS at a renowned steel plant in India had shown that EMS is only playing a supporting role to other variables like superheat and casting speed. In the current study attempt will be made to derive the optimum EMS parameters at varying superheats and casting speeds. The samples from collected billets will be evaluated using Ultrasonic C-scan imaging, macroetching and segregation studies. The results obtained will be compared with various process parameters and the threshold for producing quality high carbon billets will be arrived based on the study.