| 摘要 |
PROBLEM TO BE SOLVED: To improve can opening capability, eliminate the occurrence of break due to shock and restrict damage to a resin film layer, by specifying the steel panel thickness of the thinnest processed part of a lid panel, the position of a tab fastener, a length between the center of the tab fastener and a tab-hook grasping part, and an angle between the center line of a tab before turned and the center line of it in the position of an opening. SOLUTION: By the use of a curved-face die with a radius R of 0.1 mm-1.0 mm for the side of the surface 1a of a can lid 1 and a flat die for the side of the rear of the can lid 1, an opening groove 2 in which the cross-section of the bottom of the thinnest part 2a with a panel thickness (t) has a curved face is press-formed in a can-lid panel with a panel thickness t0 which has a resin film layer 7. Ant it is formed so as to satisfy t=5.0<P<=7.0 provided that P=t×TSx exp(n)/(nn)}×[2/(3-1/2)×|1n 1+(t-t0)}|]n, wherein n is a work hardness index in an area of 40%-90% of the uniform expansion of a steel panel forming the can lid 1, and TS (kgf/mm2) is tensile strength. Also, a tab fastener 4 is decentered and a tab 3 is turned around it.
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