| 摘要 |
<p>A tungsten electrode (35) is positioned adjacent the root face (15) of a tube (10) with the tube and the electrode being connected to a source of direct current (40) such that the electrode is positive with respect to the tube. The electrode is mounted in an assembly (30) and the assembly is provided with a shielding gas from a source (48). The electrode assembly is mounted for rotation on an orbiting head (60) with the electrode axially spaced from the root face. As the electrode is rotated about the tube, the root face (15) and a portion (20) of the inner surface and a portion (25) of the outer surface are simultaneously cathodically cleaned. Preferably, the electrode (35) cleans the root face from two to four times in preparation for a subsequent welding operation.</p> |
