[Difficult Question] What are the technical requirements for online welding of desulfurization pipelines?
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This post was last edited by hutom123 on 2009-6-15 09:12. There is a leakage at the flange of the desulfurization pipeline. What are the technical requirements for welding in situ? Generally, due to the presence of elemental sulfur in the solution, cracks occur during welding, making it difficult to complete the weld. How should this be dealt with?
Reasons for crack formation: FeS, which is formed from iron and sulfur, tends to form low-melting-point eutectics with r-Fe. When the temperature exceeds 900°C, these eutectics melt, weakening the bond between the crystal grains; this phenomenon is known as \"thermal fragility\" or \"red fragility\", and it leads to the formation of thermal cracks in the weld. Sulfides also cause segregation in steel, thereby reducing the weld’s resistance to layered tearing as well as the toughness of the steel. The main methods for controlling the sulfur content in welds are: 1. Strictly limiting the sulfur content in the base material and welding materials. Given that you are referring to welding to repair leaks, it is recommended to clean and dry the pipeline at the location of welding. First, the medium contained within the pipeline should be removed to reduce the chances of contact with sulfur during welding. The pipeline must be shut down during this process. 2. Certain elements that have a greater affinity for sulfur than iron should be added to the molten pool; these elements form sulfides, which dissolve easily in the slag but not in the metal, thereby achieving the purpose of desulfurization.