A high-performance edge heater for the hot strip mill

A transverse magnetic flux type of induction edge heater for hot strip mills that can sufficiently heat the edge portion of a transfer bar from the very head end to the very tail end was developed. This was accomplished not only by applying the magnetic flux leakageless C-type edge heater that consists of a single magnetic circuit but also by developing an algorithm for setting the optimum air gap between the upper and lower inductors and the firing angle compensation circuit. This circuit enables the main power source thyristor inverter to be operated even when the applied load is so light that the thyristor devices of the inverter cannot commutate without the circuit. Mechanical characteristics inspections of hot strips heated by the edge heater show that the elongation characteristic of the edge parts is improved from the head to the tail end of hot strips. From this it is possible to obtain uniform distribution of the elongation characteristic all along both the width and length of hot strips. Thus, the contribution of the new edge heater to the improvement of the quality and yield rate of hot strips has been confirmed