Steel plate having superior toughness in weld heat-affected zone and welded structure made therefrom

US7105066B2 · kind B2 · utility

Assignee

• POSCO CO., LTD · KR

Inventors

• Hong-Chul Jeong · Seojong-myeon, KR
• Hae-Chang Choi · Heunghae-eup, KR

Key dates

• Filing date: Nov 16, 2001
• Grant date: Sep 12, 2006
• Expiry date: Jul 14, 2022

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C21D2211/009
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

A welding structural steel product exhibiting a superior heat affected zone toughness, comprising, 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, 0.008 to 0.030% N, 0.0003 to 0.01% 0.00 1 to 0.2% W, at most 0.03% P, at most 0.03% S, at most 0.005% 0, 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, and 6.5≦(Ti+2Al+4B)/N≦14, and having a microstructure essentially consisting of a complex structure of ferrite and pearlite having a grain size of 20 μm or less. The method includes the steps of preparing a slab of the above-described composition, heating the slab to 1,100° C. to 1,250° C. for 60-180 minutes, hot rolling the heated slab in an austenite recrystallization range at a 40% or more rolling reduction followed by controlled cooling.