Abstract: Friction stir welding(FSW) is a new solid state joining technique. Generally the FSW process would apply large pressure on to workpiece which would cause deformation of either the welding equipment or the workpiece. This deformation would cause the plunge depth, a key welding parameter, deviate from its setting value, and damage the stability of the FSW process. To solve this problem, a FSW pressure control system is developed, which keeps the pressure steady by adjusting the plunge depth. The system uses a computer as top layer controller, controlling the Z axis of a FSW equipment according to the feedback of a force sensor. Using this system, butt welds of 6082-T6 aluminum alloy plates are welded on a suspended steel plate. The deformation of the 6082 plate is up to 0.931 mm during the FSW process. The produced weld shows good surface formation, uniform macro sections and mechanical properties along the weld, and the tensile strength is 222.8 MPa. The experiment result proves that the FSW pressure control system could stabilize the welding process despite the workpiece deforms under pressure.

Key words: friction stir welding, joint strength, pressure control