Effect of friction stir welding on hydrogen content of ISO 3183 X80M steel

• FSW reduces the risk of HIC in comparison to conventional fusion welding processes.
• FSW does not have a significant influence on the hydrogen concentration.
• The hydrogen pickup during FSW is not increased when the steel surfaces are oxidized.
• Hydrogen generation due to water decomposition is not expected during FSW.
• An adaptation of ISO 3690:2012 and AWS A4.3 1993 procedures to FSW is made.

The influence of Friction Stir Welding (FSW) on hydrogen content of ISO 3183 X80M high strength steel was evaluated for several welding conditions, including dry and underwater environments. The diffusible and non-diffusible (residual) hydrogen were measured by a hot extraction method that involved adaptation of ISO 3690 and AWS A4.3 (arc welding process) standards. It was found that FSW does not significantly influence the hydrogen content under dry conditions even when the steel surface is oxidized. A slight increase in both diffusible and residual hydrogen content was observed for underwater FSW. However, the total hydrogen content is significantly less than the minimum allowable hydrogen concentration in similar steels. In addition, the low tool temperature reached during underwater FSW suggests the absence of hydrogen generation by water molecule decomposition. This is in according with the temperature distribution in water obtained by finite element method simulation of this welding process. Therefore, FSW is a feasible welding process and offers important advantages in terms of hydrogen control when it is compared to conventional fusion welding processes.

Figure optionsDownload as PowerPoint slide