METHOD OF DESCALING STEEL SHEET IN COIL THROUGH HIGH DRAFT ROLLING

摘要

When a hot rolled steel sheet in coil (1) is subjected to high draft rolling by a cold rolling mill (4), crack, delamination or the like is produced in scale which cannot follow spreading of a ground steel, so that adhesion of the scale to the ground metal is degraded. When such steel sheet in coil is subjected to brushing (5), brush bristles enter into gaps produced in a scale layer, so that the scale is removed from surfaces of the steel sheet in coil. At this time, a draft R (%) is set in a manner to maintain a relationship t x R >/= 150 between the draft and a thickness of a hot rolled scale t ( mu m). The scale, of which adhesion is decreased during the high draft rolling, is removed from the surfaces of the steel sheet in coil by brush rolls (5) which are provided midway a sheet passage extending from the cold rolling mill (4) to bridle rolls. At the time of the high draft rolling, water having a large coefficient of friction or a water solution containing a water-soluble rolling oil is preferably supplied between work rolls of the cold rolling mill (4) and the steel sheet in coil (1). Since the steel sheet in coil (1) having been subjected to high draft rolling can be provided with necessary characteristics prior to pickling (8), only heat treatment after the pickling or an application of partial cold rolling makes the steel sheet in coil (1) usable as a cold rolled steel sheet in coil which is provided with the necessary characteristics.