Patent Number: 6,966,955

Title: Steel plate having TiN+ZrN precipitates for welded structures, method for manufacturing same and welded structure made therefrom

Abstract: A weldable structural steel product having TiN and ZrN precipitates, which contains, in terms of percent by weight, 0.03 to 0.17% C, 0.01 to 0.5% Si, 0.4 to 2.0% Mn, 0.005 to 0.2% Ti, 0.0005 to 0.1% Al, 0.001 to 0.03% Zr, 0.008 to 0.030% N, 0.0003 to 0.01% B, 0.001 to 0.2% W, at most 0.03% P, at most 0.03% S, at most 0.01% O, and balance Fe and incidental impurities while satisfying conditions of 1.2.ltoreq.Ti/N.ltoreq.2.5, 0.3.ltoreq.Zr/N.ltoreq.2.0, 10.ltoreq.N/B.ltoreq.40, 2.5.ltoreq.Al/N.ltoreq.7, and 6.8.ltoreq.(Ti+Zr+2Al+4B)/N.ltoreq.17, and having a microstructure essentially consisting of a complex structure of ferrite and pearlite having a grain size of 20 .mu.m or less.

Inventors: Choi; Hae-Chang (Pohang-si, KR), Jeong; Hong-Chul (Pohang-si, KR)

Assignee: Posco

International Classification: C22C 38/12 (20060101); C22C 38/04 (20060101); C22C 38/14 (20060101); C21D 8/02 (20060101); C22C 038/14 (); C22C 038/28 (); C21D 008/00 ()

Expiration Date: 1/22/02018