| 摘要 |
PURPOSE:To efficiently produce a metal pipe internally lined with resin having no air bubble or pinhole by inserting a crystalline resin pipe subjected to crystallization treatment so as to set specific resin specific gravity in a metal pipe heated to specific temp. and heating said pipe to the m.p. or higher of the resin to weld the same. CONSTITUTION:A metal pipe internally lined with resin is prepared by inserting a crystalline resin pipe in a metal pipe to weld the same under heating. After the crystalline resin pipe subjected to crystallization treatment so that resin specific gravity becomes rhoA/rhoC<=0.970 (wherein rhoA is resin specific gravity at the time of non-crystallization and rhoC is that at the time of crystallization) is inserted in the metal pipe heated so as not to exceed temp. lower by 5 deg.C than the m.p. of the resin, said resin pipe is heated to the m.p. of the resin or higher to be welded to the metal pipe. The metal pipe is heated to increase the inner diameter thereof and the resin specific gravity of the resin pipe is increased by the crystallization treatment thereof and the outer diameter of the resin pipe is contracted to smoothly perform the insert operation of the resin pipe. When the resin pipe is heated to the m.p. of the resin or more in the metal pipe, the resin becomes amorphous and the resin specific gravity becomes low and the diameter of the resin pipe is increased and the resin pipe is uniformly welded to the inner surface of the metal pipe by strong pressing force in addition to the thermal expansion, thereby the generation of the air bubbles is prevented. |
