| 摘要 |
The wall of a pressure vessel tube having stress-corrosion cracks or the like is repaired by localized melting using laser welding, for fusing over defects by melting and re-solidifying the metal. A high powered laser beam is focused at a limited area or spot on the internal wall of the tube. The welding head is operated at sufficient power and is relatively moved in the tube at a sufficient rate to melt the spot while advancing along a line on the internal surface of the wall. The wall is melted to a depth of part or all of the thickness of the wall. Points at which the tube has been melted by the focused beam cool following passage of the welding head. The welding head is also advanced laterally of the line, either continuously or stepwise. Localized melting and cooling of the tube material continues progressively, line by overlapping and/or adjacent line, to melt and reform the degraded area. By successively melting, and optionally alloying linear sections of the wall using an alloying material, stress-corrosion cracks and similar defects are fused over, repairing the degraded area. The localization of the melting is such that the metal does not substantially flow and the metal cools quickly following passage of the weld head, to below a temperature of sensitization.
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