HIGH STRENGTH API HOT-ROLLED STEEL SHEET WITH LOW YIELD RATIO FOR AMERICAN PETROLEUM INSTITUTE AND METHOD OF MANUFACTURING THE API HOT-ROLLED STEEL SHEET

摘要

PURPOSE: A high-strength API(American Petroleum Institute) hot-rolled steel sheet with a low yield ratio and a manufacturing method thereof are provided to obtain a high-strength API hot-rolled steel sheet with high tensile strength and yield strength and a low yield ratio by controlling alloy components and hot-rolling process conditions. CONSTITUTION: A method for manufacturing a high-strength API hot-rolled steel sheet is as follows. A slab panel, which comprises C(Carbon) of 0.2-0.25wt.%, Si(Silicon) of 0.1-0.3wt.%, Mn(Manganese) of 1.0-1.5wt.%, Al(Aluminum) of 0.02-0.04wt.%, Ti(Titanium) of 0.01-0.03wt.%, Ni(Nickel) of 0.05-0.3 wt.%, Cu(Copper) of 0.1-0.3wt.%, Cr(Chromium) of 0.3-0.5wt.%, Ca(Calcium) of 0.001-0.004wt.%, and Fe(Iron) and inevitable impurities, is finally rolled at an FDT(Finishing Delivery Temperature) of 800-900C. The hot-rolled panel is cooled to a CT(Coiling Temperature) of 700-600C and coiled.