Mathematical Model to Analyze Coiling Feasibility at Downcoiler in Hot Strip Mill

The coiling of a steel strip in a Downcoiler is an integrated part of the hot-rolled steel production line. Failure to coiling results damage to finished rolled strip along with mill downtime due to cobble. Thus, coiling success in Downcoiler is a critical concern for production of hot rolled steel strip. A mathematical model has been developed to analyze coiling feasibility for new grade of high strength steel to be rolled for the first time in the mill and to thereby identify a safe operating window for the coiling-process parameters. This has significant benefit in reducing the risk of coiling failure during plant trial and thus product development cycle time. The model is based on the estimation of coiler tension for a new grade with reference to mill-based physical data of coiling compactness as defined by a wrapper angle from known grades, coiled in the mill. This is followed by computation and comparison of coiling torque vis-a-vis the capacity of the Downcoiler allows a decision to be taken about the coiling feasibility of the new grade. It is believed that it is for the first time that a coiling feasibility algorithm has been developed and discussed. The model has been widely used within Tata Steel to carry out plant trails for the development of new grade as well as rolling of new section in existing grades at its Hot Strip Mill in Indian plant at Kalinganagar.