INVESTIGATIONS INTO THE HEATING CHARACTER ISTICS OF ROUGHED STRIP IN A COILBOX FURNACE

Objective. Cost-optimized hot strip production necessarily demands min imized material failure. This includes pre venting any failure of roug hed strip in the event of production disturbances. The coilbox at the entry of the finishing train in the hot wide strip mill at Bochum may, it is true, frequently serve for temporary storage of roughed strip m ade of mild steel grades, though only rarely for high-grade steels pro duced within a close temperature range, which usually cannot be furthe r processed in the rolling mill after any interruption in production. This situation is to be remedied by installing a reheating furnace at the coilbox. Summary. The coil recovery furnace has been in operation since January 1996. During 1996 around 320 roughed strips were reheate d to rolling temperature in the coil recovery furnace after production disturbances and then rolled to produce finished hot strip. This corr esponds to a production output of 5,500 t. The surface quality of the hot strip emerging from the coilbox furnace equates with grade 03. Mea surements of the roughed strip temperature profile have shown that ene rgy is withdrawn from the strip when it contacts the coil holding sadd le in the coil recovery furnace. This energy loss leads to periodic te mperature changes of up to 60 degrees C in the strip that adversely af fect the rolling characteristics in the finishing train and the final rolling thickness tolerances. Consequently, the strip emerging from th e coil recovery furnace is only finished to final thicknesses of more than 3 mm. For industrial rolling purposes a number of measures are pr oposed to improve furnace construction, e.g. by installing an inductiv e saddle heating system, a device to rotate or oscillate the coil with in the furnace, or by replacing the segment-shaped coil holding saddle by a trapezoidal saddle. (E 29738).