Steel sheet for porcelain enamel, and method of manufacturing same

Abstract

A steel sheet for porcelain enamel according to an embodiment of the present invention comprises 0.0005 to 0.0030 wt % of C, 0.15 to 0.55 wt % of Mn, to 0.03 wt % of S, 0.0001 to 0.002 wt % of Al, 0.001 to 0.020 wt % of P, 0.001 to 0.030 wt % of S, 0.02 to 0.06 wt % of Cu, 0.005 to 0.012 wt % of N, 0.05 to 0.20 wt % of Cr, and 0.03 to 0.06 wt % of O, with the balance being Fe and inevitable impurities. A cold-rolled steel sheet for porcelain enamel according to an embodiment of the present invention comprises an oxide layer that extends inward from the surface, wherein the thickness of the oxide layer is 0.006-0.030 μm.

1 . A steel sheet for porcelain enamel comprising, by weight: 0.0005 to of C, 0.15 to 0.55% of Mn, 0.001 to 0.03% of Si, 0.0001 to 0.002% of Al, 0.001 to 0.02% of P, 0.001 to 0.030% of S, 0.02 to 0.06% of Cu, 0.005 to 0.012% of N, 0.05 to 0.20% of Cr, and 0.03 to 0.06% of O, with a balance of Fe and inevitable impurities,
 wherein the steel sheet includes an oxide layer in a direction from a surface to an inside, and the oxide layer has a thickness of 0.006 to 0.030 μm.   
     
     
         2 . The steel sheet for porcelain enamel of  claim 1 , wherein:
 the following equation 1 is satisfied:
   3.05≤[Cu]/[P]≤5.10  [Equation 1]
 
   wherein [Cu] and [P] are contents (wt %) of Cu and P, respectively.   
     
     
         3 . The steel sheet for porcelain enamel of  claim 1 , wherein:
 the following Equation 2 is satisfied:
   0.032≤([Cr]/52+[Mn]/32)×([N]/14)/([C]/12)≤0.091  [Equation 2]
 
   wherein [Cr], [Mn], [N], and [C] are contents (wt %) of Cr, Mn, N, and C, respectively.   
     
     
         4 . The steel sheet for porcelain enamel of  claim 1 , further comprising:
 one or more of 0.001 wt % or less of Ti, 0.001 wt % or less of Nb, 0.02 wt % or less of Ni, 0.001 wt % or less of V, and 0.02 wt % or less of Mo.   
     
     
         5 . The steel sheet for porcelain enamel of  claim 1 , wherein:
 the following Equation 3 is satisfied:
   0.45≤( R   a ×50× S   e )/ P   c ≤0.99  [Equation 3]
 
   wherein P c  is the number of surface irregularities per unit centimeter (cm), R a  is an average roughness value (μm), and S e  is a temper reduction rate (%).   
     
     
         6 . The steel sheet for porcelain enamel of  claim 1 , wherein:
 a yield strength after an enamel firing heat treatment is 220 MPa or more.   
     
     
         7 . The steel sheet for porcelain enamel of  claim 1 , wherein:
 an enamel adhesiveness is 95% or more.   
     
     
         8 . The steel sheet for porcelain enamel of  claim 1 , wherein:
 a hydrogen permeation ratio is 600 sec/mm 2 or more.   
     
     
         9 . A method of manufacturing a steel sheet for porcelain enamel, the method comprising:
 hot rolling a slab including, by weight: 0.0005 to 0.0030% of C, 0.15 to 0.55% of Mn, 0.001 to 0.03% of Si, 0.0001 to 0.002% of Al, 0.001 to 0.020% of P, 0.001 to 0.030% of S, 0.02 to 0.06% of Cu, 0.005 to 0.012% of N, 0.05 to 0.20% of Cr, and 0.03 to 0.06% of O, with a balance of Fe and inevitable impurities to manufacture a hot rolled steel sheet;   cold rolling the hot rolled steel sheet to manufacture a cold rolled steel sheet;   annealing the cold rolled steel sheet; and   temper rolling the annealed cold rolled steel sheet,   wherein the annealing is performed at a temperature of 760 to 840° C. for 10 to 90 seconds.   
     
     
         10 . The method of manufacturing a steel sheet for porcelain enamel of  claim 9 , wherein:
 in the manufacturing of a hot rolled steel sheet,   a finish hot rolling temperature is 910 to 970° C.   
     
     
         11 . The method of manufacturing a steel sheet for porcelain enamel of  claim 9 , wherein:
 in the manufacturing of a hot rolled steel sheet,   a winding temperature is 580 to 720° C.   
     
     
         12 . The method of manufacturing a steel sheet for porcelain enamel of  claim 9 , wherein:
 in the manufacturing of a cold rolled steel sheet, a reduction rate is 60 to 90%.   
     
     
         13 . The method of manufacturing a steel sheet for porcelain enamel of  claim 9 , wherein:
 the temper rolling is rolled at a reduction rate 0.4 to 2.0%.   
     
     
         14 . The method of manufacturing a steel sheet for porcelain enamel of  claim 9 , further comprising:
 after the temper rolling, enamel firing the temper rolled steel sheet at a temperature of 780 to 850° C.