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A challenging weld repair of Grade 91 tubing by avoiding PWHT
Documento en inglés, elaborado por la Empresa Laborelec y BWI (Belgian Welding Institute), en el que se investiga sobre la posibilidad de emplear la técnica Cold Weld Repair, con el fin de evitar usar gases de purga y tratamiento térmico, en las reparaciones de soldaduras de P91
Autores: S. Huysmans y J. Vekeman
Nº de páginas: 12
Grade 91 pipes and tubes have become a standard material for the design of new and refurbishment of existing Power Plants. Several major failures have been encountered after fabrication of these new Creep Strength Enhanced (CSE) steels and are mainly attributable to improper practices. Another critical situation however is arising when it comes to repair welding. Gas backing and the required PWHT are a time consuming factor in the total weld repair schedule. While PWHT is a prerequisite for obtaining the correct microstructure, power generators will tend to avoid this thermal treatment in order to reduce down-time of the power plant.
In a collaborative research program, the BWI and Laborelec undertook the challenge to investigate the feasibility of a Cold Weld Repair methodology in order to weld repair T91 tubes without the use of gas backing and PWHT. The feasibility study so far demonstrated that a repair method based on the selection of an undermatched consumable and a controlled deposition procedure can result in an acceptable microstructure and hence inherent properties.
The results of the research program are very promising for temporary repair welding of T91 tubes within the containment of the boiler.