Method for supplying rolling oil for cold rolling

A method for supplying rolling oil for cold rolling, comprising:

• supplying emulsion rolling oil using both:
• (i) a first rolling oil supply system supplying the emulsion rolling oil to a roll and a steel sheet being rolled in a recirculation mode, and (ii) a second rolling oil supply system supplying the emulsion rolling oil to only the front and back surface of the steel sheet being rolled, wherein the emulsion rolling oil supplied by the second rolling oil supply system comprise an emulsifier of a same type but lower concentration as an emulsifier of the first rolling oil supply system, and second rolling oil system is controlled so that an average particle diameter of emulsion is larger than an average particle diameter of emulsion of the first rolling oil supply system;
• recovering the emulsion of the second rolling oil supply system which has not stuck onto the steel sheet being rolled, adding an emulsifier to the recovered emulsion so that the concentration of the emulsifier is equal to that of the emulsifier of the first rolling oil supply system, and mechanically agitating the emulsion of the second rolling oil supply system;
• and
• joining the emulsion of the second rolling oil supply system, having been agitated mechanically, to the emulsion of the first rolling oil supply system.