Welding heat treatment process for repair of long-term service P92 steel

Abstract

The invention relates to a welding heat treatment process for repair of long-term service P92 steel, and belongs to the technical field of steel material repair. In the welding process adopted by the invention, when the first layer of cladding metal in contact with the base metal is welded, the welding heat input is obviously increased. The main reason is that the peak temperature of heat circulation in the welding process is higher under the larger heat input. Under the influence of the welding temperature, large precipitates in a heat affected zone, especially in a coarse grain zone, are remelted at the temperature, fine dispersed carbides can be re-separated out from a saturated solid solution formed after the precipitates are remelted in subsequent cooling and heat treatment, and finally, the impact toughness of the heat affected zone is improved under the action of dispersion strengthening and second phase strengthening. By means of the process, the impact toughness of a welding joint, especially the welding heat affected zone, can be greatly improved compared with base metal, and application and popularization of the process are particularly important for guaranteeing the performance of the welding joint and further guaranteeing safe and stable operation of a unit.

Description

technical field [0001] The invention relates to a welding heat treatment process for the repair of long-serving P92 steel, which belongs to the technical field of rigid material repair. Background technique [0002] At present, in order to meet the operating requirements of the unit with high steam parameters, the materials for the high-temperature components of the unit need to meet the following requirements: better processing performance, lower thermal expansion coefficient, thermal fatigue resistance, good welding performance and high cost performance. P92 steel has better high-temperature strength and high-temperature oxidation resistance, lower linear expansion coefficient, better thermal fatigue resistance and less intergranular corrosion, and is the main material for high-temperature components of ultra-supercritical 1000MW units. [0003] However, the impact toughness of the base material is severely reduced after long-term service (generally more than 50000h). Thi...

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Problems solved by technology

[0008] Due to the previous welding process, there is no special welding process for the replacement or repair of this type of material, which will lead to poor impact toughness of the welded joint, especially the heat-affected zone, which cannot meet the requirements of relevant standards

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