| 摘要 |
<p>Disclosed are a hot rolled steel sheet for an oil pipeline satisfying an API X80 standard while having a low yield ratio of 80% or less based on the thickness of 10 mm by controlling an alloy component and a process condition; and a method to manufacture the same. According to the present invention, the method to manufacture the hot rolled steel sheet comprises: a step of re-heating a slab comprising, by wt%, 0.05-0.15% of carbon (C), 0.2-0.5% of silicon (Si), 1.7-2.2% of manganese (Mn), 0.03% or less of phosphorus (P), 0.01% or less of sulfur (S), 0.01% or less of nitrogen (N), 0.06-0.12% of niobium (Nb), 0.01-0.05% of titanium (Ti), 0.1-0.5% of nickel (Ni), 0.1-0.5% of chrome (Cr), 0.1-0.5% of molybdenum (Mo), and the remainder consisting of iron (Fe) and inevitable impurities at 1200-1300°C which is a slab reheating temperature (SRT); a step of hot rolling the re-heated slab at 780-860°C which is a finishing delivery temperature (FDT); and a step of coiling the hot rolled slab at 530-630°C which is a coiling temperature (CT).</p> |
