| 摘要 |
PURPOSE:To obtain an extremely thick steel plate having sound and uniform quality without preliminary forging by specifying the hydrogen content and segregation element value of a unidirectionally solidified ingot and limiting a rolling method. CONSTITUTION:The hydrogen content in a unidirectionally solidified ingot is regulated to <=1.5ppm, the segregation element B value expressed by the equation I to <=0.2 and the thickness to >=400mm.. In the equation I , (x); the length on the long side of a billet, (y); the length on the short side of the billet, (a); the max. width of the area where inverted V segregation is formed. Such unidirectionally solidified ingot is rolled in such a way that the sum Seff value of the effective rolling stress in the direction perpendicular to the central part of the thickness expressed by the equation II is regulated to >=0.1 in the stage of <4 total rolling ratio. In the equation II, sigmatcmax; the max. compressive stress in the direction perpendicular to the central part of the plate thickness, K0; the pure deformation resistance. |
