Method of drawing and ironing a resin film laminated metal sheet and resin film laminated drawn and ironed can using the same method
A method of drawing and ironing a resin film laminated metal sheet for forming a can body having a bottom portion, a can wall portion and a flange-forming portion by drawing the resin film laminated metal sheet obtained by laminating at least one surface of a metal sheet with an organic resin film, followed by ironing by using a punch and a plurality of dies neighboring each other. The can wall is effectively prevented from being broken by a decrease in the thickness of the can wall, and drawn and ironed cans are efficiently formed having a thickness which is decreased as designed.
1. A method of drawing and ironing a resin film laminated metal sheet for forming a can body having a bottom portion, a can wall portion and a flange-forming portion by drawing the resin film laminated metal sheet obtained by laminating at least one surface of a metal sheet with an organic resin film, followed by ironing by using a punch, having a front end oriented toward the bottom of the can and a rear end, and a plurality of ironing dies neighboring each other,
wherein the punch has no taper at a position corresponding to the flange-forming portion and has a taper formed at a position corresponding to the can wall portion that is continuous to the flange-forming portion, said taper comprises a two-stage taper including a first taper having a first taper angle and a second taper continuing to the rear end portion of the first taper and having a second taper angle different from that of the first taper angle, the first taper having a length greater than a distance between the land of a first ironing die and the land of a final ironing die of the plurality of ironing dies, and the diameter of the taper increasing toward the bottom of the can.
2. A method of drawing and ironing according to claim 1 , wherein said punch has a small-diameter portion at a rear end portion thereof, and effects the ironing in a manner that the ratio of ironing is 0 to 15% at the open end of the can body that is formed.
3. A method of drawing and ironing according to claim 2 , wherein said plurality of dies are arranged as neighboring dies in succession.
4. A method of draw-ironing according to claim 2 , wherein the ratio of ironing is 0 to 10% at the open end of the can body that is formed.
5. A method of drawing and ironing according to claim 1 , wherein said plurality of dies are arranged as neighboring dies in succession.
6. A drawn and ironed can made by the method as claimed in claim 1 , said drawn and ironed can having a bottom portion, a can wall portion and a flange-forming portion formed by drawing and ironing a resin-coated metal sheet obtained by laminating at least one surface of a metal sheet with an organic resin film, wherein the inner surface of the can wall portion continuous to the flange-forming portion is tapered in a manner that the thickness decreases from the upper side toward the lower side starting from the lower portion of the flange-forming portion, and no step is formed on the outer surface of the can wall portion.
7. A method of draw-ironing according to claim 1 , wherein said taper comprises a two-stage taper including a first taper having a first taper angle and a second taper continuing to the rear end portion of the first taper and having a second taper angle different from that of the first taper angle.
8. A method of draw-ironing according to claim 7 , wherein the first taper has a length that is greater than the distance between the land of the first ironing die and the land of the final ironing die by 1 to 30 mm.
9. A method of draw-ironing according to claim 7 , wherein the second taper angle is greater than the first taper angle.
10. A method of draw-ironing according to claim 1 , wherein the distance between the land of the first ironing die and the land of the final ironing die is from 3 to 40 mm.
11. A method of draw-ironing according to claim 1 , wherein the distance between the land of the first ironing die and the land of the final ironing die is from 3 to 20 mm.