MANUFACTURE OF ACCELERATEDLY COOLED STEEL SHEET HAVING SMALL RESIDUAL STRESS

摘要

PURPOSE:To manufacture a steel sheet having small residual stress without losing strength increasing effect by accelerated cooling by acceleratedly cooling a hot rolled steel plate from a specified temp. under specified conditions and carrying out rolling with a leveler. CONSTITUTION:A low carbon steel billet is hot rolled and the resulting steel plate is acceleratedly cooled from (the Ar3 point-70 deg.C) or above at >=3 deg.C/sec cooling rate CR and a finished cooling temp. FCT ( deg.C) satisfying FCT<=500log(CR) to produce >=15kgf/mm<2> residual stress in the surface of the steel plate. This steel plate is then rolled with a leveler. An acceleratedly cooled steel sheet having <=10kgf/mm<2> residual stress, superior strength, toughness, weld crack resistance and superior toughness of the weld heat-affected zone is manufactured.