| 摘要 |
PURPOSE:To improve DI (draw and ironing) formability and corrosion resistance by providing the polyester resin film with specified properties on at least one surface of a steel sheet. CONSTITUTION:The polyester resin film in which any one property or both properties of the crystallization heat (Hc) at low temperature of at most 7cal/g and the fusion heat (Hf) of at most 10cal/g are sufficient value, and then its density is 1.370 or lower, and its weight-average molecular weight is 700,000 or lower, is laminated on the surface corresponding to at least inner surface of the can of a steel sheet, thereby obtaining an aimed composite steel sheet. As the means for laminating the polyester resin film on the steel sheet, the process in which the film is pressure-bonded under heating onto the steel sheet, and further it is heated to the temperature equal to the melting point of the resin or higher and is rapidly cooled by dipping it in water, is used. This composite steel sheet has the excellent formability for continuous DI, and its corrosion resistance is remarkably improved, whereby a single coat-DI can and further uncoated DI can according to its content may be used, though conventionally the double coat of its inner surface is necessary for the DI can of steel base. |
