Fiction Stir Welding of 5083-H131 Aluminum Alloy using A2 and H13 Tool Steels or 420 Stainless Steel Tooling

Abstract

Friction Stir Welding (FSW) is a solid state welding method developed by The Welding Institute. The process is environmentally friendly, highly repetitive and easily adapted to manufacturing geometries. New welding schedules are being continuously developed for materials that are traditionally difficult to join by fusion welding methods (e.g. TIG/MIG/Stick). This experiment develops the welding schedule and process parameters for acceptable welds in 5083-H131 aluminum using three different tool materials (A2 and H13 tool steel along with 420 Stainless Steel). The mechanical properties of all friction stir welds were compared against standard MIG welds (from a qualified industrial facility) and the as-delivered parent material. All of the friction stir welds greatly outperformed the MIG welds. The welds produced by the H13 tool were statistically identical in bending to the original parent material. None of the friction stir welds performed more poorly than the MIG during ultimate tensile testing. The friction stir weld produced by the 420 SS tool was by far the best weld in terms of tensile strength. Equipment limitations (motor horsepower) may have prevented achieving a friction stir weld equal to or better than the parent material. All friction stir welds exhibited uniform hardness results across the weld that was much higher than the MIG welds hardness. None of the friction stir welds exhibited the porosity of the MIG welds when cross-sectioned.

The FSW machine used was actually a CNC mill that lacked the horsepower to extend the test to higher RPM/Feeds. Technical guidelines were developed (as an Appendix) from the lessons learned for the university research technician attempting to develop a welding schedule with a three-axis CNC machine not intended for friction stir welding.