Abstract: A hot rolling line and a hot rolling method capable of finer refining crystal grains are provided. Specifically, the hot rolling line for a metal sheet is composed of a finish rolling mill, a leveler, and a cooling apparatus installed from upstream to downstream in this sequence in a metal sheet transporting direction. The hot rolling method is such that, in the above hot rolling line, a metal sheet obtained by finish rolling a metal piece is subjected to repeated bending processing by the leveler and then cooled.

Abstract: A process control apparatus and a process control system for observing the waveform of the deviation between a set point which controls the process in a control loop and the process controlled variable transmitted from the process so that the operating parameters are adjusted in accordance with a predetermined adjustment rule by using the deviation based upon the absolute value of a wave for every half cycle of the wave. Therefore, even if the process controlled variable is influenced, the area of the wave cannot be changed significantly. As a result, the operating parameters can be adjusted correctly, causing the process controlled variable to quickly coincide with the set point.