A New Tension Control Method for Hot Strip Finishing Mill

NKK has developed a new tension control method for the hot strip finishing mill, and applied it to Keihin Works. The behavior of the interstand tension by the looper control was evaluated by simulation and it was concluded that the mass moment of looper inertia should be reduced drastically. To achieve this, a full stand looperless rolling technique using statistical scheme was developed for the large-sectioned material use. Hence, loopers were scaled down by 2/3 only for the small-sectioned material use, and the optimum looper control technique under modern control theory was applied. Consequently, a 40% reduction in the longitudinal thickness variation of the product strip has been achieved.