High-strength hot-rolled plated steel sheet and method for manufacturing the same

Abstract

Disclosed is a high-strength hot-rolled plated steel sheet capable of suppressing material deterioration at the time of plating, while having high strength, and a method for manufacturing the same. The high-strength hot-rolled plated steel sheet may include: a hot-rolled steel sheet base material composed of 0.03-0.1 wt % of C, below 0.06 wt % of Si, 0.7-2.0 wt % of Mn, below 0.02 wt % of P, below 0.01 wt % of S, 0.1-0.5 wt % of one or more precipitate forming elements, 0.3-1.0 wt % of Al, 0.1-0.5 wt % of Mo, Fe, and unavoidable impurities; and a plated layer formed on the surface of the hot-rolled steel sheet base material.

1 . A method for manufacturing a high-strength hot-rolled plated steel sheet, comprising:
 (a) reheating a slab composed of 0.03-0.1 wt % of carbon (C), below 0.06 wt % of silicon (Si), 0.7-2.0 wt % of manganese (Mn), below 0.02 wt % of phosphorous (P), below 0.01 wt % of sulfur (S), 0.1-0.5 wt % of one or more precipitate forming elements, 0.3-1.0 wt % of aluminum (Al), 0.1-0.5 wt % of molybdenum (Mo), steel (Fe), and unavoidable impurities, the precipitate forming elements forming a precipitate at 500 to 900° C;   (b) hot-rolling the slab;   (c) cooling the hot-rolled slab, and then winding the cooled slab; and   (d) plating the wound slab.   
     
     
         2 . The method of  claim 1 , further comprising the step of alloying the slab having the plated layer formed thereon. 
     
     
         3 . The method of  claim 1 , wherein the step of hot rolling the slab comprises:
 roughing rolling the reheated slab at 950 to 1,050° C.; and   finishing rolling the roughing-rolled slab at a finishing temperature condition of 800 to 900° C.   
     
     
         4 . The method of  claim 1 , wherein the step of cooling the hot-rolled slab, and the winding the cooled slab comprises cooling the hot-rolled slab at an average cooling speed of 100° C./sec or more, and then winding the cooled slab at 580 to 660° C. 
     
     
         5 . The method of  claim 1 , wherein the step of plating the wound slab comprises uncoiling and pickling the wound slab, and hot-dip plating the slab without a heat treatment at a temperature of Ac1 or more. 
     
     
         6 . The method of  claim 1 , wherein the precipitate forming element comprises at least one of 0.03-0.1 wt % of niobium (Nb), 0.03-0.1 wt % of titanium (Ti), and 0.08-0.3 wt % of vanadium (V). 
     
     
         7 . The method of  claim 1 , wherein the precipitate forming element comprises 0.03-0.1 wt % of Nb, 0.03-0.1 wt % of Ti, and 0.08-0.3 wt % of V. 
     
     
         8 . A high-strength hot-rolled plated steel sheet comprising:
 a hot-rolled steel sheet base material composed of 0.03-0.1 wt % of C, below 0.06 wt % of Si, 0.7-2.0 wt % of Mn, below 0.02 wt % of P, below 0.01 wt % of S, 0.1-0.5 wt % of one or more precipitate forming elements, 0.3-1.0 wt % of Al, 0.1-0.5 wt % of Mo, Fe, and unavoidable impurities, the precipitate forming elements forming a precipitate at 500 to 900° C.; and   a plated layer formed on the surface of the hot-rolled steel sheet base material,   wherein the high-strength hot-rolled plated steel sheet exhibits a tensile strength of 780 to 900 MPa, a yield strength of 700 to 850 MPa, an elongation of 14 to 22%, and a hole expansion of 55% or more.   
     
     
         9 . The high-strength hot-rolled plated steel sheet of  claim 8 , wherein the hot-rolled steel sheet base material of the hot-rolled plated steel sheet has a microstructure which is composed of a ferrite single-phase structure and in which fine precipitates having a size of less than 10 nm are formed. 
     
     
         10 . The high-strength hot-rolled plated steel sheet of  claim 8 , wherein the precipitate forming element comprises at least one of 0.03-0.1 wt % of Nb, 0.03-0.1 wt % of Ti, and 0.08-0.3 wt % of V. 
     
     
         11 . The high-strength hot-rolled plated steel sheet of  claim 8 , wherein the precipitate forming element comprises 0.03-0.1 wt % of Nb, 0.03-0.1 wt % of Ti, and 0.08-0.3 wt % of V.