| 摘要 |
PURPOSE: A method for manufacturing a hot rolled mild steel sheet that exhibits superior grain structure homogeneity in width profile by addition of a trace amount of boron and then properly controlling coiling temperature after hot rolling is provided. CONSTITUTION: The method includes the steps of hot rolling a slab comprising C 0.02 to 0.05 wt.%, trace Si, Mn 0.10 to 0.30 wt.%, B 10 to 30 ppm, 0.015 wt.% or less of P, 0.010 wt.% or less S, Al 0.01 to 0.04 wt.% and 40 ppm or less of N to the thickness of 1.3 to 2.3 mm, wherein finish hot rolling temperature is higher than Ar3 transformation temperature; coiling the hot rolled steel sheet at higher than 620 deg.C; pickling the hot coil to remove surface scale; and applying oil on the surface of the pickled steel sheet.
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