STEEL PLATE OR SHAPE STEEL FOR HIGH TOUGHNESS AND HIGH STRENGTH BOLTING SPLICE PLATE, EASY OF CUTTING AND BOLTHOLE PUNCHING

摘要

PROBLEM TO BE SOLVED: To obtain a steel plate for high strength bolting splice plate, having prescribed thickness and easy of cutting, bolthole punching, and surface grooving, by specifying the composition, consisting of C, Si, Mn, Al, S, and Fe, and hardness of a surface layer, respectively, and also specifying the C content and hardness of the central part, respectively. ;SOLUTION: The surface layer, in the region between the surface and a position at a depth of 0.2-1.0 mm from the surface in a plate-thickness direction, has a composition consisting of, by weight, 0.20-0.50% C, 0.03-2.0% Si, 0.25-2.5% Mn, 0.002-0.10% Al, 0.002-0.05% S, and the balance Fe with inevitable impurities and further containing, if necessary, prescribed amounts of Nb, Ti, Cu, Ni, Cr, Mo, Co, W, V, B, Rem, Ca, and Mg and also has ≥360 Vickers hardness. Further, the central part, between a position of 2.0 mm above the center of plate thickness and a position of 2.0 mm below the center of plate thickness in a plate thickness direction, has C content lower by 0.03-0.2% than the C content of the surface layer and also has ≤300 Vickers hardness. By regulating the thickness of this steel sheet to 6-25 mm and applying grooving to the surface layer part, the splice plate, having stable and high coefficient of sliding of a friction grip jointing plane, can be easily obtained.;COPYRIGHT: (C)1998,JPO