Optimisation of electromagnetic stirring in continuously cast steel billets using ultrasonic C-scan imaging technique

Abstract

The present paper presents the analysis of ultrasonic C-scan images obtained through an automatic computerised multiscan immersion system, to obtain optimum current and frequency of an electromagnetic stirrer (EMS), installed at Billet Caster-1 of LD Shop-1 of M/s Tata Steel Ltd, Jamshedpur. The purpose was to achieve minimum defects and maximum equiaxed zones in the continuously cast steel billets. The amplitudes and positional data were integrated and controlled by a PC based ultrasonic equipment. The defect size and area in C-scan image was calculated automatically by a labelling and clustering algorithm, which showed a good correlation to the condition of actual defects. One low carbon steel Grade-A and one high carbon Grade-A were selected for experimental trials. The experiments conducted with various current and frequency combinations revealed that in general, quality of continuously cast steel billets improved with increasing EMS current in both grades of steel considered in the present work. The most significant improvement was found at 280 A EMS current and frequency 3.5 Hz. Beyond this there was only a marginal improvement in the billet quality as well as equiaxed zone. Based on the experimental observations, it is recommended to operate EMS at 280 A current and EMS frequency at 3.5 Hz in the plant.