| 摘要 |
<p>The method of forming a seamed metal tube (20c) having a metal coating (56) of this invention includes galvanizing the strip (20) prior to welding. The strip (20) is then formed into an open seam tube (20b) and welded in an inert atmosphere with the seam (71) located in the lower portion of the tube. Finally, the metal coating (56) is caused to flow downwardly over the seam (71), coating the seam (71) by several means. In one embodiment, the strip (20) is preformed into an arcuate shape (20a) and galvanized, wherein the zinc coating (56) increases in thickness toward the lateral strip edges (48), such that the coating (56) will flow over the seam (71) following welding. The tube (20c) may also be reheated following welding, preferably in an enclosure (78) containing an inert atmosphere which includes the weld apparatus (62). In another embodiment, an inert gas is directed over the inner and outer surfaces of the tube (20c), adjacent the seam (71), driving the molten metal downwardly over the seam (71) to coat the seam (71). In another embodiment, the lateral edges (48) of the strip (20) are formed with indentions or grooves (188) directed toward the lateral edges (48) which direct the molten metal downwardly over the seam (71).</p> |
