A method of manufacturing a laser cutting the steel and the steel is excellent in laser cutting

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PROBLEM TO BE SOLVED : To provide production conditions for a steel plate capable of obtaining excellent cutting quality in laser cutting and suitable for being provided to shipbuilding, civil engineering, building, bridges, construction and industrial machinery, marine structures, storage tanks, pressure vessels or the like, and to provide a steel plate.SOLUTION : A cast slab or a billet including, by mass, 0.05 to 0.20% C, 0.01 to 0.40% Si, 0.1 to 1.6% Mn, 0.005 to 0.030% P and ≤0.01% S, and, if necessary, including one or more kinds selected from Cu, Ni, Cr, Mo, Nb, V, Ti, B, rare earth metals, Ca and Mg, and the balance Fe with inevitable impurities is reheated at 1, 000 to 1, 200°C, thereafter, before the start of hot rolling, the surface and back surface of the steel plate are jetted with water to perform descaling, immediately before a rolling pass between 1, 000°C and a rolling finishing temperature, the surface and back surface are again jetted with water to perform descaling for three or more times, and hot rolling finished at 800 to 950°C is performed, thereafter, it is air-cooled in the air, and is gradually cooled in the range from 550 to 150°C to room temperature at <0.05°C/s in the temperature range of the total ≥100°C. The steel plate has the above componential composition, and in which the average thickness of surface scales in the steel plate is 10 to 40 μm, and also, the total content of FeOand FeO in the surface scales is controlled to ≥80mass%.