Steel sheet for enamel having no surface defects and method of manufacturing the same
A steel sheet for enameling for eliminating surface defects such as fish scale defects and having excellent formability, and provides a steel sheet for enamel having no surface defects, including: more than 0 wt % and 0.005 wt % or less of C, 0.1 to 0.5 wt % of Mn, more than 0 wt % and 0.03 wt % or less of Si, 0.05 to 0.3 wt % of Cr, more than 0 wt % and 0.03 wt % or less of Al, 0.03 to 0.1 wt % of O, more than 0 wt % and 0.03 wt % or less of P, more than 0 wt % and 0.02 wt % or less of S, more than 0 wt % and 0.015 wt % or less of Cu, more than 0 wt % and 0.005 wt % or less of N, Fe in a remaining content, and other inevitable impurities.
1. A steel sheet for enamel having no surface defects, comprising:
more than 0 wt % and 0.005 wt % or less of C, 0.1 to 0.5 wt % of Mn, more than 0 wt % and 0.03 wt % or less of Si, 0.05 to 0.3 wt % of Cr, more than 0 wt % and 0.03 wt % or less of Al, 0.03 to 0.1 wt % of O, more than 0 wt % and 0.03 wt % or less of P, more than 0 wt % and 0.02 wt % or less of S, more than 0 wt % and 0.015 wt % or less of Cu, more than 0 wt % and 0.005 wt % or less of N, Fe in a remaining content, and other inevitable impurities,
where the steel sheet includes Cr—Mn complex oxides.
2. The steel sheet for enamel having no surface defects of claim 1 , wherein:
an atomic ratio of Cr/Mn in the Cr—Mn complex oxides is in the range of 0.01 to 2.
3. The steel sheet for enamel having no surface defects of claim 2 , wherein:
a size of the Cr—Mn complex oxides is 1 to 25 μm.
4. The steel sheet for enamel having no surface defects of claim 3 , wherein:
the number of the Cr—Mn complex oxides is 1.5×10 2 or more per 1 mm 2 of an observation view.
5. A method of manufacturing a steel sheet for enamel having no surface defects, comprising:
manufacturing a slab formed of more than 0 wt % and 0.005 wt % or less of C, 0.1 to 0.5 wt % of Mn, more than 0 wt % and 0.03 wt % or less of Si, 0.05 to 0.3 wt % of Cr, more than 0 wt % and 0.03 wt % or less of Al, 0.03 to 0.1 wt % of O, more than 0 wt % and 0.03 wt % or less of P, more than 0 wt % and 0.02 wt % or less of S, more than 0 wt % and 0.015 wt % or less of Cu, more than 0 wt % and 0.005 wt % or less of N, Fe in a remaining content, and other inevitable impurities;
manufacturing a hot rolled steel sheet by hot rolling after the slab is re-heated to 1,200° C. or more; and
winding the hot rolled steel sheet at 550° C. or more,
wherein, after winding, the hot rolled steel sheet includes Cr—Mn complex oxides.
6. The method of manufacturing a steel sheet for enamel having no surface defects of claim 5 , further comprising:
performing cold rolling at a reduction ratio of 50 to 90% after the winding.
7. The method of manufacturing a steel sheet for enamel having no surface defects of claim 6 , further comprising:
performing continuous annealing of the cold rolled steel sheet at 700° C. or more for 20 sec or more after the cold rolling.
8. The method of manufacturing a steel sheet for enamel having no surface defects of claim 5 , wherein:
an atomic ratio of Cr/Mn in the Cr—Mn complex oxides is 0.01 to 2.
9. The method of manufacturing a steel sheet for enamel having no surface defects of claim 8 , wherein:
in the steel sheet for enamel manufactured by the method of manufacturing the steel sheet for enamel, a size of the Cr—Mn complex oxides is 1 to 25 μm.
10. The method of manufacturing a steel sheet for enamel having no surface defects of claim 9 , wherein:
in the steel sheet for enamel manufactured by the method of manufacturing the steel sheet for enamel, the number of the Cr—Mn complex oxides is 1.5×10 2 or more per 1 mm 2 of an observation view.
11. The method of manufacturing a steel sheet for enamel having no surface defects of claim 10 , wherein:
in the steel sheet for enamel manufactured by the method of manufacturing the steel sheet for enamel, micro-voids are formed in the Cr—Mn complex oxide itself or a periphery thereof.
12. The method of manufacturing a steel sheet for enamel having no surface defects of claim 6 , wherein:
an atomic ratio of Cr/Mn in the Cr—Mn complex oxides is 0.01 to 2.
13. The method of manufacturing a steel sheet for enamel having no surface defects of claim 7 , wherein:
an atomic ratio of Cr/Mn in the Cr—Mn complex oxides is 0.01 to 2.