The cold rolling steel sheet null for deep drawing which is superior in chemical conversion coating Characteristic and resistance liquid metal

摘要

PURPOSE:To provide the above cold rolled steel sheet for deep drawing which take advantage of the excellent characteristics, such as elongation and r value, of the extra-low C cold rolled steel sheet having a prescribed component compsn. by regulating the average C concn. and max. C concn. in the thickness direction after annealing of the extra-low C cold rolled steel sheet. CONSTITUTION:The cold rolled steel sheet contg., by weight %, =0.005% C, =1.0% Si, =1.0% Mn, =0.2% P, =0.05% S, 0.01 to 0.10% Al, and =0.005% N is annealed. The C concn. distribution in the thickness of the resulted annealed sheet is such that the average C concn. is 0.05 to 0.1% in the layer of the thickness corresponding to one ferrite average grain size from the surface of the steel sheet. The max. C concn. of this steel sheet is 0.01 to 0.2%. The annealed sheet is the cold rolled steel sheet for deep drawing which is produced by continuous annealing preferably from the extra-low C steel sheet and has the excellent chemical conversion treatability and liquid metal bittleness resistance at the time of a painting stage.