A high performance edge heater for the hot strip mill

A transverse magnetic flux type of induction edge heater for the hot strip mill which can heat the edge portion of a transfer bar from the heat end to the tail end was developed. The edge heating system consists of a single magnetic circuit. An algorithm for setting the optimum air gap between the upper and lower inductors and firing-angle compensation circuit were developed. 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 it. Inspections of the mechanical characteristics of hot strips heated by the edge heater show that the elongation characteristic of the edge parts was improved from the head to the tail, so that it is possible to obtain a uniform distribution of the elongation characteristic along both the width and length of hot strips. The contribution of the edge heater improving the quality and yield of hot strips has been confirmed.<>