| 摘要 |
PURPOSE:To obtain a corrosion-proof coated steel tube, which is covered with band-shaped covering material by helically lap-winding it with no air gaps left between lapped materials by a method wherein adhesive layer which is formed onto the band-shaped covering material by piling up adhesive continuously and parallel to the longitudinal direction of the band-shaped material so as to produce a composite sheet, is connected by helically lap-winging the composite sheet so as to contact the adhesive layer of the composite sheet with itself with no air gaps left at the end part of the lap-winding. CONSTITUTION:First, a steel tube 1 is heated so as to melt modified polyethylene adhesive powder, which is uniformly coated to 0.05-0.1mm thickness onto the tube by means of an electrostatic powder coater or the like, in order to form the film of an adhesive layer 2. Secondly, a composite sheet 6 with an adhesive layer 5 formed thereonto is produced by piling up adhesive onto a band-shaped covering material 4. The composite sheet 6 is heated to be softened and melted so as to be able to lap-wind it in order to join the covering material 4 to itself and to join the covering material 4, the adhesive layer 5 and the covering material 4 to one another in the order named by means of the pressing forces of rollers 3a and 3b. At the same time, the piled-up adhesive layer 5 fills air gap portions 7 so as to become the main body 9 of connection in order to form the connecting layer of pinching film by coming into contact with the adhesive layer 2 on the surface of the steel tube 1 into an combined body. In this case, with the rotation of the steel tube 1, said connecting layer of pinching film is continuously formed simultaneously with the covering with the covering material 4. |
