| 摘要 |
PROBLEM TO BE SOLVED: To strongly weld a ring regardless of existence of zinc on a tube surface by using shield gas with CO2 and O2 mixed with Ar, at the time of welding by press-fitting the ring on the outer periphery of the inserting hole of a cast iron tube. SOLUTION: The ring 12 is press-fitted onto the outer periphery of the inserting hole 9 of the cast iron tube 8. The ring 12 is constituted of a cylindrical body and formed with an outer peripheral groove 15 on this outer periphery and the thickness at the bottom part 16 of this outer peripheral groove 15 is made thin as much as possible. Further, the part 17 in the ring 12 corresponding to the tip side of the inserting hole 9 is projects from the part 18 corresponding to the tube barrel part side. At the time of press-fitting the ring 12 to the position where the end surface 21 of the ring 12 is on the same surface with the tip part 22 of the inserting hole 9, molten metal is poured into the outer peripheral groove 15 of the ring while rotating the tube 8 to melt the bottom part 16 of the outer peripheral groove 15 and the surface part of the inserting hole 9. At this time, as the shield gas, the gas with CO2 or oxygen mixed with Ar is used. By this method, the sufficient detaching preventing performance is given to a tube joint. |
