Draw-ironed steel can and method of producing the same
A seamless can including a resin-coated steel plate. The can is a draw-ironed steel can having a resin coating formed on at least the inner surface of the can, wherein the resin coating on the inner surface of the can has a tensile strength of 160 to 360 MPa. Also disclosed is a method of producing the draw-ironed steel can.
1. A draw-ironed steel can obtained by draw-ironing a resin-coated steel plate having an unstretched and unoriented resin coating formed on at least the surface that becomes the inner surface of the can, wherein
the resin coating of the draw-ironed can has a two-layer constitution comprising a surface layer of a highly crystalline polyester resin and a lower layer of a lowly crystalline polyester resin, the ratio of thicknesses of the surface layer and the lower layer being 1:1 to 4:1;
the highly crystalline polyester resin is an ethylene terephthalate type polyester resin in which an isophthalic acid is copolymerized in an amount of 0 mol % and less than 3 mol %, and the lowly crystalline polyester resin is an ethylene terephthalate type polyester resin in which the isophthalic acid is copolymerized in an amount of 13 to 17 mol %; and
the resin coating on the inner surface of the can has a tensile strength of 240 to 300 MPa.
2. A method of producing a draw-ironed steel can by draw-ironing a resin-coated steel plate having an unstretched and unoriented resin coating formed on at least the surface that becomes the inner surface of the can,
the resin-coating having a two-layer constitution comprising a surface layer of a highly crystalline polyester resin and a lower layer of a lowly crystalline polyester resin, the ratio of thicknesses of the surface layer and the lower layer being 1:1 to 4:1, the highly crystalline polyester resin being an ethylene terephthalate type polyester resin in which an isophthalic acid is copolymerized in an amount of larger than 0 mol % and less than 3 mol %, and the lowly crystalline polyester resin being an ethylene terephthalate type polyester resin in which the isophthalic acid is copolymerized in an amount of 13 to 17 mol %; and
by setting the drawing ratio in a range of 1.1 to 2.6, the ironing ratio in a range of 50 to 80%, and using a punch of which the temperature is adjusted to be 20 to 50° C.