Hydrogen generation for sensing and control in submerged friction stir welding

Abstract

Friction stir welding (FSW) is a recently developed welding technique, where the metals that are welded are not melted. FSW takes place at temperatures below the solidus points of the metals that are joined. FSW is thus a solid-state process. This can yield weldments of a significantly higher strength than those achieved by traditional fusion welding processes. This is due to the enhanced grain structure of the FSW materials. Submerged FSW is performed underwater for structural purposes such as oil platforms and pipelines, or in industrial settings and laboratories in order to further enhance the strength of the weldments, sometimes exceeding the strength of the parent materials. Submerged FSW, due to the significantly lower temperatures of the process compared to FSW in air, yields even more enhanced grain structures and greater strengths. In the experiments performed here, it is shown that the hydrogen generated during submerged FSW is produced at rates and quantities sufficient to be easily detected by means of a fuel cell. The generated hydrogen, which is a function of the FSW parameters, can be used as a means of sensing and control of submerged FSW which can be applied to robotic and automatic submerged FSW.