STEEL SHEET WITH SMALL WELDING DEFORMATION AND EXCELLENT CORROSION RESISTANCE

摘要

Disclosed is a steel sheet with small welding deformation and excellent corrosion resistance, which is characterized by having a chemical composition containing, in mass%, 0.02-0.25% of C, 0.01-0.7% of Si, 0.3-2% of Mn, 0.05% or less of P, 0.008% or less of S, less than 0.2% of Cu, 1-2.5% of Cr, 0.05% or less of Mo, 0.005-0.1% of Nb, 0.003-0.1% of Al, 0.01% or less of N and 0.03-0.50% of Sn, with the balance made up of Fe and impurities and a Cu/Sn ratio of 1 or less. The steel sheet is also characterized in that the metallic structure thereof is composed of 10-60% of a ferrite structure and 40-90% of a bainite structure and/or a martensite structure, the ferrite structure has an average particle diameter of 30 µm or less, and the ratio of the hardness of the bainite structure and/or the martensite structure to the hardness of the ferrite structure is 1.5 or more. The steel sheet may additionally contain one or more substances selected from among Ti, Ni, V, B, Zr, Ca, Mg and REM.