PURPOSE: To check the overcooling of a rolling material and to prevent the generation of a slip during rolling caused by the formation of secondary scales, by spraying a low-pressure atomized water on a rolling material at a rough rolling line and a high-pressure atomized water at intermediate and finish rolling lines.

CONSTITUTION: A rolling material W of free-cutting steel discharged from a heating furnace H is passed through a rolling stage consisting of a rough rolling line and intermediate and finish rolling lines, to roll-form it into a final shape. A train of low-pressure descalers D1 and high-pressure descalers D2, D3 are provided to the rough rolling line and the intermediate and finish rolling lines. Low-pressure water e.g. ≥4kg/cm2 water, is sprayed at the rough rolling line because of its low rolling speed, on the other hand, high-pressure water e.g. about 50W100kg/cm2 water is sprayed at the intermediate and finish rolling lines because of their high rolling speeds to remove the secondary scales respectively.