| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a steel sheet which can attain excellent cutting quality when performing laser-cut and is suited for use in e.g., shipbuilding. <P>SOLUTION: The steel sheet has a composition comprising specified amounts, by mass%, of C, Si, Mn, P, S, Al, N, O, Po, defined by the below-shown formula, of -5 to 25, optionally at least one element of Cu, Ni, Cr, Mo, Nb, V, Ti, B, REM, Ca, and Mg, and the balance being Fe and unavoidable impurities, has an average scale layer thickness of 10 μm or less, contains 60 mass% or more of magnetite in the scale layer, and more desirably, has a standard deviation of the scale thicknesses of 4.0 μm or less. A cast slab or a billet comprising the steel composition is reheated to 1,000-1,200°C and subjected to hot rolling so as to finish at 650-850°C. During a rolling pass between 950°C and the rolling finish temperature, the steel sheet is subjected to descaling of jetting water onto the top and back surfaces of the steel sheet at least 5 times at a time interval of 10-50 seconds between descaling passes. Po=(2.9Si-0.2Mn+0.7Al)×(O-0.0023)<SP POS="POST">2</SP>×10<SP POS="POST">7</SP>, wherein Si, Mn, Al, and O stand for their respective contents (mass%). <P>COPYRIGHT: (C)2012,JPO&INPIT |
