Steel sheet and manufacturing method therefor

Abstract

The present invention relates to a steel sheet that can be used in automobiles, etc., and relates to a steel sheet that can ensure improved plating characteristics, and a manufacturing method therefor.

1 . A steel sheet comprising:
 one or two of Mn and Si in steel,   wherein, in a glow discharge optical emission spectrometer (GDS) profile in which one or two components of Mn and Si are observed in a depth direction from a surface of the steel sheet, the steel sheet comprises two or more valleys in which amounts of the one or two components of Mn and Si are 60% or less of an amount of a parent material within 1 μm from the surface of the steel sheet.   
     
     
         2 . The steel sheet of  claim 1 , wherein amounts of the one or two of Mn and Si included in a grain or a grain boundary within 1 μm in the depth direction from the surface are 40% or more of an amount of each of the components in the parent material. 
     
     
         3 . The steel sheet of  claim 1 , wherein the steel sheet comprises an oxide formed of one or two or more of Mn, Si, Al, Cr, and B is included in a grain boundary within 10 μm from the surface in the depth direction. 
     
     
         4 . The steel sheet of  claim 1 , wherein the steel sheet comprises, by weight, C: 0.02 to 0.6%, Si: 0.001 to 2%, Al: 0.001 to 1%, Mn: 0.1 to 4%, P: 0.05% or less, S: 0.02% or less, Cr: 1% or less, N: 0.02% or less, Ti: 0 to 0.1%, B: 0.0001 to 0.01%, Cu: 0 to 1.00%, Mo: 0 to 1.00%, Cr: 0 to 1.00%, Ni: 0 to 1.00%, V: 0 to 1.00%, Ca: 0 to 0.01%, Nb: 0 to 0.1%, Sn: 0 to 1%, W: 0 to 1%, Sb: 0 to 1%, Mg: 0 to 0.1%, Co: 0 to 1%, As: 0 to 1%, Zr: 0 to 1%, Bi: 0 to 1%, REM: 0 to 0.3%, the remainder Fe, and unavoidable impurities. 
     
     
         5 . The steel sheet of  claim 1 , wherein the steel sheet comprises a hot-dip galvanized layer or a hot-dip aluminum-plated layer formed on the surface. 
     
     
         6 . A method for manufacturing a steel sheet, comprising:
 preparing a base steel sheet comprising one or two of Mn and Si in steel;   forming an Fe plating layer by performing Fe pre-plating on a surface of the base steel sheet with a thickness of more than 0.5 g/m 2  to 3 g/m 2  or less; and   annealing the base steel sheet on which the Fe plating layer has been formed, at a temperature of 600 to 950° C. in an atmosphere having a dew point temperature of 10° C. or less.   
     
     
         7 . The method of  claim 6 , wherein the Fe pre-plating is performed by electroplating. 
     
     
         8 . The method of  claim 6 , wherein a period in time for the annealing is 1 to 1000 seconds. 
     
     
         9 . The method of  claim 6 , wherein moist nitrogen is injected at a flow rate of 50 to 200 Nm 3 /h during heating for the annealing. 
     
     
         10 . The method of  claim 6 , wherein the base steel sheet comprises, by weight, C: 0.02 to 0.6%, Si: 0.001 to 2%, Al: 0.001 to 1%, Mn: 0.1 to 4%, P: 0.05% or less, S: 0.02% or less, Cr: 1% or less, N: 0.02% or less, Ti: 0 to 0.1%, B: 0.0001 to 0.01%, Cu: 0 to 1.00%, Mo: 0 to 1.00%, Cr: 0 to 1.00%, Ni: 0 to 1.00%, V: 0 to 1.00%, Ca: 0 to 0.01%, Nb: 0 to 0.1%, Sn: 0 to 1%, W: 0 to 1%, Sb: 0 to 1%, Mg: 0 to 0.1%, Co: 0 to 1%, As: 0 to 1%, Zr: 0 to 1%, Bi: 0 to 1%, REM: 0 to 0.3%, the remainder Fe, and unavoidable impurities. 
     
     
         11 . The method of  claim 6 , wherein the base steel sheet is manufactured by comprising reheating a steel slab to a temperature range of 1200° C. or higher;
 hot-rolling at a finish-rolling temperature of Ar3 to 1000° C. after the reheating; 
 coiling at a temperature range more than a martensite start temperature (Ms) to 750° C. or less; and 
 cold-rolling at a cumulative reduction ratio of 30 to 90%. 
 
     
     
         12 . The method of  claim 6 , further comprising forming a plating layer by immersing the steel sheet in a hot-dip galvanizing bath or a hot-dip aluminum plating bath after the annealing.