| 摘要 |
PURPOSE:To improve the strength of a welded joint by preheating the weld zone at a specified temp. before stress relief annealing so as to prevent or reduce the softening of the weld heat-affected zone. CONSTITUTION:This invention relates to the heat treatment of the weld zone of a pipe, especially a 9Cr-1Mo-Nb-V steel pipe for a thermoelectric power plant. The weld zone is preheated at 400-650 deg.C before stress relief annealing. By the preheating, the internal strain causing the acceleration of the softening of the weld heat-affected zone during annealing is relieved or eliminated, so the softening of the weld heat-affected zone by the following stress relief annealing is prevented or reduced.
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