| 摘要 |
PURPOSE:To prevent thinning down of resin-coating at a weld bead part and obtain the titled metal tube firmly adhered with resin, by pressing only resin of an adhesive layer under heating after preheating a metal tube piece having a weld bead, coating thermoplastic resin, cooling and solidifying. CONSTITUTION:A metal tube piece having a bead is heated to the temperature T1 deg.C which satisfies the melting point of thermoplastic resin used for coating (e.g. polyethylene etc.) plus ta deg.C and 0<=ta<=40. Then, a thermoplastic resin film is coated to the preheated tube piece, e.g. being extruded by a T die method etc. and wound, sent immediately to a cooling zone by rotating carry and support rolls etc., cooled and solidifed. Then a resin-coated metal tube piece is e.g. passed through an induction heating ring of frequency 30Hz-50kHz, pressed by a roll etc. from outside, heating only the tube piece at the temperature T2 deg.C which satisfies the melting point of the resin of an adhesive layer contacting to the tube piece +tb deg.C and 10<=tb<=100, thus the desired metal tube is obtained. |
