| 摘要 |
PURPOSE: Provided is a manufacturing method of thin hot coil with yield strength 22-24kg/mm¬2, tensile strength 32-33kg/mm¬2, and elongation rate over 46% for the application to deep drawing works. CONSTITUTION: In hot-rolling a steel slab comprising C 0.02-0.03wt.%, trace amount of Si, Mn 0.05-0.15wt.%, Cr 0.2-0.5wt.%, P 0.015wt.% or less, Al 0.02-0.04wt.%, and N2 < 40ppm in a thickness of 1.3 to 2.3mm, finish rolling is performed over Ar3 transformation temperature. Also, coiling temperature after hot-rolling is regulated to be higher than 650°C. In this method, Cr is added to steel for the purpose of lowering Ar3 transformation temperature, and both ends of a bar are heated by an edge heater right before finish rolling to compensate temperature losses so that this thin hot coil has excellent properties for deep drawing.
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