TREATMENT OF HOT ROLLED STEEL STOCK

摘要

PURPOSE:To prevent the transformation of FeO to Fe3O4 and to permit easy descaling by subjecting a rolled steel stock after hot finish rolling to rolling down or bending at a limited temp. and draft and cooling quickly the stock down to a limited temp. during or right aftet the working. CONSTITUTION:The hot-rolled steel strip 2 at about 900 deg.C emitted from a hot finishing stand 1 is cooled to >=570 deg.C in a conveying stage and is subjected to light rolling down at 0.1-15% by a rolling mill 3. The sheet 2 in the temp. state of 570 deg.C is thereafter quickly cooled at >=30 deg.C/min cooling rate by a water cooling device 4 consisting of cooling water sprays until about 300 deg.C is attained. The sheet 2 at about 200 deg.C is coiled by a coiler 5. The steel is thus cracked 6 in the state of obviating the transformation of FeO to Fe3O4 and the steel is cooled with the water in the same state. As a result, the cooling water W infiltrates to the FeO layer through the cracks 6 by which the sheet is cooled to <=300 deg.C and the FeO layer remains. The taken-up coil is descaled prior to cold rolling.