Hot-rolled steel sheet having excellent composite corrosion resistance to sulfuric acid and hydrochloric acid and manufacturing method therefor

Abstract

Provided are a hot-rolled steel sheet having high composite corrosion resistance to sulfuric acid and hydrochloric acid, and a method for manufacturing the hot-rolled steel sheet. According to an aspect, the hot-rolled steel sheet having high composite corrosion resistance to sulfuric acid and hydrochloric acid includes, by wt %, carbon (C): 0.05% to 0.1%, manganese (Mn): 0.5% to 1.5%, phosphorus (P): 0.02% or less, sulfur (S): 0.02% to less, aluminum (Al): 0.01% to 0.1%, copper (Cu): 0.2% to 0.6%, antimony (Sb): 0.05% to 0.1%, and a balance of iron (Fe) and inevitable impurities, wherein copper (Cu) and antimony (Sb) are concentrated in a region from a surface to a 500-nm position in a thickness direction of the hot-rolled steel sheet, and the hot-rolled steel sheet has a corrosion loss of 2.0 mg/cm 2 /hr or less in a solution of 16.9 volume % sulfuric acid and 0.35 volume % hydrochloric acid.

1 . A hot-rolled steel sheet having high composite corrosion resistance to sulfuric acid and hydrochloric acid, the hot-rolled steel sheet comprising, by wt %, carbon (C): 0.05% to 0.1%, manganese (Mn): 0.5% to 1.5%, phosphorus (P): 0.02% or less, sulfur (S): 0.02% or less, aluminum (Al): 0.01% to 0.1%, copper (Cu): 0.2% to 0.6%, antimony (Sb): 0.05% to 0.1%, and a balance of iron (Fe) and inevitable impurities, wherein copper (Cu) and antimony (Sb) are concentrated in a region from a surface to a 500-nm position in a thickness direction of the hot-rolled steel sheet, and the hot-rolled steel sheet has a corrosion loss of 2.0 mg/cm 2 /hr or less in a solution of 16.9 volume % sulfuric acid and 0.35 volume % hydrochloric acid. 
     
     
         2 . The hot-rolled steel sheet of  claim 1 , wherein the inevitable impurities comprise tungsten (W), molybdenum (Mo), cobalt (Co), and nickel (Ni) in a total amount of less than 10 ppm. 
     
     
         3 . The hot-rolled steel sheet of  claim 1 , wherein the concentrated copper (Cu) and antimony (Sb) form an oxide layer comprising a Cu—Sb composite oxide in a corrosive environment containing sulfuric acid and hydrochloric acid. 
     
     
         4 . The hot-rolled steel sheet of  claim 3 , wherein the oxide layer has a thickness of 400 nm to 500 nm from the surface of the hot-rolled steel sheet in the thickness direction of the hot-rolled steel sheet. 
     
     
         5 . A method for manufacturing a hot-rolled steel sheet having high composite corrosion resistance to sulfuric acid and hydrochloric acid, the method comprising:
 reheating a steel slab to 1100° C. to 1300° C., the steel slab comprising, by wt %, carbon (C): 0.05% to 0.1%, manganese (Mn): 0.5% to 1.5%, phosphorus (P): 0.02% or less, sulfur (S): 0.02% or less, aluminum (Al): 0.01% to 0.1%, copper (Cu): 0.2% to 0.6%, antimony (Sb): 0.05% to 0.1%, and a balance of iron (Fe) and inevitable impurities;   obtaining a hot-rolled steel sheet by hot rolling the reheated steel slab and finish hot rolling the steel slab at a temperature of 850° C. to 950° C.;   rapidly cooling the hot-rolled steel sheet at a rate of 120° C./s to 150° C./s;   coiling the cooled hot-rolled steel sheet at a temperature of 650° C. to 750° C.; and   slowly cooling the coiled hot-rolled steel sheet at a rate of 30° C./hr to 40° C./hr to a cooling finish temperature of 350° C. to 400° C.   
     
     
         6 . The method of  claim 5 , wherein during the coiling of the cooled hot-rolled steel sheet, a surface of the hot-rolled steel sheet reaches a temperature of 720° C. to 750° C. through a heat recuperation phenomenon.