| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of manufacturing a multiple coated steel pipe formed by covering an outer surface of an anti-corrosion layer formed on the outside of a steel pipe with a protective layer having adhesion and peelability.SOLUTION: In a multiple coated steel pipe 1, on the outside of a steel pipe 1 as a base material, an anti-corrosion layer 300 comprising a polyethylene resin layer, and a protective layer 400 comprising a polypropylene layer as an upper layer of the anti-corrosion layer 300, are formed. In manufacturing the multiple coated steel pipe 1, after the steel pipe 1 is coated with polyethylene resin, a surface temperature of the polyethylene resin is cooled to 40 to 70°C, to form the anti-corrosion layer 300. Specific polypropylene resin is used for coating the surface of the anti-corrosion layer 300, so that a temperature of the polypropylene resin keeps 260 to 290°C and coating thickness is 0.9 to 1.8 mm. A surface temperature of the polypropylene resin is cooled to 170°C or lower at cooling speed of 153 to 450°C/sec, to form the protective layer 400. |
