| 摘要 |
PURPOSE: Provided is a method for manufacturing hot rolled steel sheets having superior uniform elongation property and aging resistance where a trace amount of boron is added to steel and temperature condition of coiling process is controlled to be suitable for manufacturing high quality hot rolled steel sheets. CONSTITUTION: The hot rolled steel sheet is manufactured by reheating a steel slab comprising C 0.02-0.05wt.%, Mn 0.10-0.30wt.%, B 10-30ppm, P 0.020wt.% or less, Al 0.01-0.04wt.%, N 40ppm or less, a balance of Fe, and other inevitable impurities; finish hot rolling the steel slab to 1.4-2.3mm at over Ar3 transformation point; and then coiling it in the temperature range of 600 to 700deg.C. The obtained steel sheet has physical properties as follows: yield strength=<22kg/mm2, tensile strength=<34kg/mm2, elongation rate>=45%, aging index(A.I)=<1kg/mm2.
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