| 摘要 |
<p>PURPOSE: A hot rolled steel sheet with high spiral weldability for a line pipe and a manufacturing method thereof are provided to prevent insufficient yield strength resulting from Bauschinger effect after spiral welding by adding Nb(Niobium) and Ca(Calcium). CONSTITUTION: A method for manufacturing a hot rolled steel sheet for a line pipe comprises a step of finish-rolling a slab to an FDT(Finishing Delivery Temperature) of 850±20°C and a step of cooling and coiling the hot rolled sheet at a CT(Coiling Temperature) of 600±20°C. The slab comprises C(Carbon) of 0.04-0.07wt.%, Si(Silicon) of 0.1-0.2wt.%, Mn(Manganese) of 0.8-1.3wt.%, P(Phosphorus) of 0.02wt.% or less, S(Sulfur) of 0.003wt.% or less, Nb of 0.03-0.15wt.%, Ca of 0.002-0.0045wt.%, and Fe(Iron) and inevitable impurities of the remaining amount.</p> |
