Speed and load modes of rolling hollow billet at the wide-strip rolling mill

The paper considers load modes of rolling heavy strips of difficult-to-form steel grades in the continuous widestrip rolling mill. It provides results obtained at the experimental study of load modes of the mill stand electric drives at the rolling strips of new gauges at OJSC Magnitogorsk Iron and Steel Works´ 2,000 mm rolling mill. It is shown that at low rolling speeds shock loading may result in inadmissible decrease in speed of rolls and shutdown of the mill stand. To eliminate adverse effects the method of intense increase of roll speed before the strip entry into the mill stand is proposed. It has been proved that minimum permissible rolling speeds may be decreased due to the mill stands when this method is realized. The functional chart of the unit implementing the developed method in the electric drives of the roughing mill group stands is considered. Results of experiment carried out at 2,000 mm mill stand are provided. It has been confirmed that the static error of the speed control may be compensated in the steady-state mode of rolling.