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Can friction stir welding be used under water, oil or other liquid?


Friction stir welding (FSW) is a solid state joining process invented by TWI in 1991. Most weld geometries that are possible in conventional fusion welding are equally achievable in FSW and some of them are actually easier. For example, as FSW does not cause any melting of the metal, it is equally as easily performed vertically, upside down and even under water, oil or other liquid. The FSW process conducted under water, oil or other liquid is called as submerged FSW (S-FSW).

The most recent research at TWI is to develop S-FSW process for internal repair of live oil pipelines. The initial welding trials has established by assessing the weld specimens that the S-FSW process had not only produced a consolidated weld but, equally importantly, had not caused an uptake of hydrocarbons into the weld zone as shown in Figure 1.

Can friction stir welding be used under water, oil or other liquid

Figure 1. Macroscopic cross-section of the weld specimen made using an 8mm probe length into a 28mm wall thickness, API-X65 steel pipe. The weld was performed under oil and is consolidated.

More information on internal weld repair of live oil pipelines

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