| 摘要 |
<p>Disclosed are steel sheets cable of being utilized as a material for line pipes due to excellent hydrogen-induced cracking resistance and a manufacturing method thereof. The steel sheets according to the present invention are characterized in weight % by comprising; carbon (C) : 0.055~0.07%, silicon (Si) : 0.2~0.3%, manganese (Mn) : 1.3~1.6%, phosphor (P) : less than 0.01% , phosphor (S) : less than 0.001% , aluminum (Al) : 0.02~0.05 %, nickel (Ni) : 0.2~0.5%, chromium (Cr) : 0.2~0.3%, niobium (Nb) : 0.03~0.05%, vanadium (V) : 0.02~0.05%, titanium (Ti) : 0.01~0.02%, calcium (Ca) : 0.002~0.004% and a balance of iron (Fe) and unavoidable impurities, and having a combined structure of acicular ferrite as the primary phase and bainite as the secondary phase. [Reference numerals] (AA) START; (BB) END; (S110) Slab reheating step; (S120) Hot rolling step; (S130) Cooling step</p> |
