Cold rolled steel sheet for continuous type self-brazing and manufacturing method therefor

Abstract

(In Equations (1) and (2), [B], [Al] and [N] denote percent by weights of B, Al, and N.)

1 . A continuous self-brazing cold rolled steel sheet comprising 0.02 wt % to 0.08 wt % of C, 0.03 wt % to 0.10 wt % of Mn, 0.10 wt % or less of Si (excluding 0 wt %), 0.005 wt % to 0.05 wt % of Al, 0.015 wt % or less of P (excluding 0 wt %), 0.01 wt % or less of S (excluding 0 wt %), 0.005 wt % or less of N (excluding 0 wt %), 0.0003 wt % to 0.0036 wt % of B, a remainder Fe, and other inevitable impurities, and satisfying Equations (1) and (2),
 wherein an average crystal grain size is 8 μm to 16 μm.
   0.15≤([B]/10.81)/([Al]/26.98)  [Equation 1]
 
   0.8≤([B]/10.81)/([N]/14.01)≤1.6  [Equation 2]
 
   (In Equations (1) and (2), [B], [Al] and [N] denote percent by weights of B, Al and N).   
     
     
         2 . The continuous self-brazing cold rolled steel sheet of  claim 1 , wherein a weight ratio of AlN precipitates and BN precipitates satisfies Equation (3),
   {[BN]/(10.81+14.01)}/{[AlN]/(26.98+14.01)}≥1  [Equation 3]
   (In Equation (3), [BN] and [AlN] denote percent by weights of the BN precipitates and the AlN precipitates).   
     
     
         3 . The continuous self-brazing cold rolled steel sheet of  claim 1 , wherein a weight ratio of N, the AlN precipitates, and the BN precipitates, existing in steel in a solid solution state, satisfies Equation (4).
   ([N]/14.01)/{[AlN]/(26.98+14.01)+[BN]/(26.98+14.01)}≤0.1  [Equation 4]
   (In Equation (4), [N], [BN] and [AlN] denote a solid solution amount (wt %) of N, and percent by weights of the BN precipitates and the AlN precipitates).   
     
     
         4 . A method of manufacturing a continuous self-brazing cold rolled steel sheet, the method comprising:
 Heating, at 1200° C. or more, a slab including 0.02 wt % to 0.08 wt % of C, 0.03 wt % to 0.10 wt % of Mn, 0.10 wt % or less of Si (excluding 0 wt %), 0.005 wt % to 0.05 wt % of Al, 0.015 wt % or less of P (excluding 0 wt %), 0.01 wt % or less of S (excluding 0 wt %), 0.005 wt % or less of N (excluding 0 wt %), 0.0003 wt % to 0.0036 wt % of B, a remainder Fe, and other inevitable impurities, and satisfying Equations (1) and (2);   manufacturing a hot rolled steel sheet by hot rolling the heated slab;   winding the hot rolled steel sheet;   manufacturing a cold rolled steel sheet by cold rolling the wound hot rolled steel sheet; and   annealing the cold rolled steel sheet at 600° C. to 850° C.
   0.15≤([B]/10.81)/([Al]/26.98)  [Equation 1]
 
   0.8≤([B]/10.81)/([N]/14.01)≤1.6  [Equation 2]
 
   (In Equations (1) and (2), [B], [Al] and [N] denote percent by weights of B, Al and N.)   
     
     
         5 . The method of  claim 4 , wherein in the heating of the slab, the slab is heated at 1230° C. to 1350° C. 
     
     
         6 . The method of  claim 4 , wherein in the manufacturing of the hot rolled steel sheet, a finish rolling temperature ranges from 875° C. to 1050° C. 
     
     
         7 . The method of  claim 4 , wherein in the winding of the hot rolled steel sheet, a winding temperature ranges from 600° C. to 750° C. 
     
     
         8 . The method of  claim 4 , wherein in the manufacturing of the cold rolled steel sheet, cold rolling is performed at a reduction rate of 50% to 95%. 
     
     
         9 . The method of  claim 4 , wherein in the annealing, continuous annealing is performed for 20 seconds to 600 seconds at 600° C. to 850° C. 
     
     
         10 . The method of  claim 4 , wherein in the annealing, batch annealing is performed for 5 hours to 72 hours at 600° C. to 800° C. 
     
     
         11 . The method of  claim 4 , wherein in the manufactured cold rolled steel sheet, a weight ratio of AlN precipitates and BN precipitates satisfies Equation (3),
   {[BN]/(10.81+14.01)}/{[AlN]/(26.98+14.01)}≥1  [Equation 3]
   (In Equation (3), [BN] and [AlN] denote percent by weights of BN precipitates and AlN precipitates.)   
     
     
         12 . The method of  claim 4 , wherein a weight ratio of N, the AlN precipitates, and the BN precipitates, existing in the manufactured cold rolled steel sheet in a solid solution state, satisfies Equation (4).
   ([N]/14.01)/{[AlN]/(26.98+14.01)+[BN]/(26.98+14.01)}≤0.1  [Equation 4]
   (In Equation (4), [N], [BN] and [AlN] denote a solid solution amount (wt %) of N, and percent by weights of the BN precipitates and the AlN precipitates)   
     
     
         13 . A copper plated steel sheet comprising a base steel sheet formed by the cold rolled steel sheet of  claim 1  and a copper plated layer coated on a surface of the base steel sheet. 
     
     
         14 . The copper plated steel sheet of  claim 13 , wherein a depth, by which the plated layer is penetrated into the cold rolled steel sheet, is 2.5 μm or less.