Patent ID: 6946038
Filing Date: 2005-09-20
Classification: C21D,C22C

Abstract:
1. A weldable structural steel product having fine complex precipitates of TiN and MnS, comprising, in terms of percent by weight, 0.03 to 0.17% C, 0.01 to 0.5% Si, 1.0 to 2.5% Mn, 0.005 to 0.2% Ti, 0.0005 to 0.1% Al, 0.008 to 0.030% N, 0.0003 to 0.01% B, 0.001. to 0.2% W, at most 0.03% P, 0.003 to 0.05% S, at most 0.005% O, and balance Fe and incidental impurities while satisfying conditions of 1.2≦Ti/N≦2.5, 10≦N/B≦40, 2.5≦Al/N≦7, 6.5≦(Ti+2Al+4B)/N≦14, and 220≦Mn/S 400, and having a microstructure essentially consisting of a complex structure of ferrite and pearlite having a grain size of 20 μm or less and wherein said precipitates of TiN and MnS have a grain size of 0.01 to 0.1 μm and are dispersed at a density of 1.0×10 7 /mm 2 or more with a spacing of 0.5 μm or less.