METHOD FOR MANUFACTURING OF HIGH STRENGTH AND HIGH FORMABILITY DUAL PHASE STEEL AND GALVANIZED STEEL SHEET

摘要

PURPOSE: A cold-rolled steel sheet with high stiffness and high formability and a method for manufacturing the same are provided to ensure high productivity and good surface quality by satisfying the mechanical property of DP(Dual Phase) steel of 780MPa at a CVGL(Continuous Vertical Galvanizing Line). CONSTITUTION: A method of manufacturing a cold-rolled steel sheet with high stiffness and high formability is as follows. A steel slab is re-heated at a SRT(Slab Reheating Temperature) of 1150~1250°C. The steel slab is hot-rolled at a FDT(Finishing mill Delivery Temperature) of 800~900°C, and thus a hot-rolled steel sheet is formed. The hot-rolled steel sheet is wound at a CT(Coiling Temperature) of 550~650°C, and thus a hot-rolled steel sheet coil is formed. The hot-rolled steel sheet coil is pickled and cold-rolled, and thus a cold-rolled steel sheet is formed. The cold-rolled steel sheet is hot-dipped and galvanized at an AT(Annealing Temperature) of 770~830°C, and thus a cold-rolled steel sheet with a dual phase structure is formed.