Development and Qualification of a Production Capable FSW Process for 25 mm Deep Robotic Friction Stir Welds

摘要

A production capable FSW process has been developed for a 25.4 mm penetration butt weld in 6061-T6 Aluminum alloy. The process was developed specifically for robotic welding application, since many of the weld paths are multi-dimensional. This process has been used in production for the last year to assemble and join complex assemblies with approximately 15 meters of weld per assembly. The following conclusions have been drawn from this work 1) Robotic FSW machines using standard industrial robots are capable of creating welds with penetrations up to one inch. This is a significantly higher depth of penetration than previously thought possible. 2) Low welding force processes (< 10 kN thrust force) can be developed for material 25 mm in thickness. 3) A stable FSW process was developed that could withstand in excess of 10 percent variation from nominal operating condition of the critical parameters (rotation speed, travel speed, and welding thrust force). 4) The developed process was shown to be stable with gap conditions ranging from 0 millimeters up to 1 millimeter. 5) It was shown that zero degree tilt FSW tools must be used with caution in production applications due to sensitivity to gap conditions. 6) Pre-drilled starter holes are not necessary for welds with up to 25 mm penetration. 7) A repair process was developed that involved plugs and multi-pass welding with less than a 10 percent loss in tensile strength 8) The FSW process is more sensitive to part mis-location on the retreating side of the FSW tool. This has significant ramifications for FSW process control and specifications and needs to be considered in these documents.