TWI Industrial Member Report Summary 684/1999
C J Dawes, E J R Spurgin and D G Staines
Friction stir welding (FSW) can achieve high quality butt welds in 5xxx series (Al-Mg) aluminium alloys. The welding speed, however, is slow when compared to welding the 6xxx series (Al-Mg-Si) alloys; typically 100mm/min compared to at least 30mm/min when making single pass welds in 6mm thick plate.
The 5xxx series alloys, especially alloy 5083, has wide use for shipbuilding and marine structures. These applications usually require long continuous welds and consequently any reduction in welding time, by increasing welding speed, will reduce production costs.
TWI invented and patented FSW in the autumn of 1991. Subsequently the process was developed under a Group Sponsored Project (GSP) 5651 in which a tool (GSP tool) and welding schedules were developed for welding various Al alloy sheet and plate at 1.5-12mm thickness.
The FSW tool technology is the most important part of the FSW process, since in essence the tool material, profile and dimensions determine the weld quality and welding speed. The GSP tool that was perfected for welding aluminium alloy 5083 gives a high and repeatable weld quality at a modest welding speed (110mm/min). This report describes work to develop a tool which will give higher welding speeds whilst maintaining the weld quality.
- To increase welding speed, whilst maintaining good weld quality, when making FSW butt joints between 6mm thick aluminium alloy 5083-O plate.