| 摘要 |
PURPOSE:To manufacture a plastic-coated steel pipe having an improved strength of plastic coating, by making close the distance between a water-cooling starting point for the plastic-coated steel pipe in the half-melted state and the lip port of a round die, and by cooling said steel pipe with water. CONSTITUTION:While a bonding agent is extruded from a round die 7' tightly connected to a bonding agent extruder 6', a half-melted plastic extruded from a round die 7 for common extrusion tightly connected to a plastic extruder 6 is applied on the outer surface of a steel pipe 1 to form a plastic coating 8, and this is cooled down by a water-cooling device 10. For the water-cooling, a water- cooling device 10' is disposed so that the distance l2 between the lip port of the round die 7 and a water-cooling starting point be 30-150mm.. |
