| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of hot-dip metal coating on the external surface of a steel tube, capable of manufacturing a metal coated steel tube by means of ordinary continuous metal coated steel tube manufacturing equipment by using plug devices where the coming-off of the plugs can be prevented even if air is expanded because of the reduced amount of air within the steel tube and also buoyancy is small and the immersion of the steel tube can be done without forcing it into a plating bath, in a plating method where plugs are inserted into both ends of a steel tube and then the steel tube is immersed in a plating bath. SOLUTION: A core 4, having a length corresponding to that of a steel tube 1 to be plated, is allowed to penetrate into the steel tube. The ends of the steel tube are closed by fitting plug bodies 3 which have insertion holes 5 for the core, respectively, to the core from respective end sides of the steel tube. Then, the steel tube is immersed in a hot-dip metal coating bath to undergo plating. It is desirable that the plug bodies which close the ends of the steel tube are temporarily welded to the steel tube and to the core, in the position between the steel tube and the core.
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