Method of descaling steel sheet in coil through high draft rolling

When a hot-rolled steel strip 1 is rolled at a large rolling reduction by a cold-rolling mill 4, cracking and interlayer peeling occur in those mill-scales which can not keep up with the elongation of base steel so as to weaken the adhesiveness of the mill-scales to the base steel. When such a steel strip is then brushed, the threads of the brush penetrate into the cracks formed in the scale layer, whereby the mill-scales are removed from the steel strip. The rolling reduction R (%) is set to satisfy the formula of t x R >/= 150 in relation with the thickness t ( mu m) of the mill-scales. The mill-scales weakened in adhesiveness by the heavy-duty rolling are removed from the surface of the steel strip 1 by brush rolls 5 provided in the pass of the steel strip 1 between the cold-rolling mill 4 and the bridle rolls 5. Water or a water-soluble rolling oil having a large friction coefficient is preferably supplied to the roll bites between work rolls of the cold-rolling mill 4 and the steel strip 1 during the heavy-duty rolling. Since the steel strip 1 is given required properties by the heavy-duty rolling in advance of pickling 8, it is used as a cold-rolled steel strip having the required properties simply by heat treatment or slight cold-rolling after pickling.