During the friction process, one workpiece is fixed by the fixture, and the other workpiece moves back and forth in a straight line with it. Under the push of the axial feeding mechanism, the two strip welding surfaces contact and rub with each other. With the friction movement and axial advancement, the friction surface generates friction heat, and the surface metal gradually reaches the viscoplastic state. Under the action of axial pressure, it deforms and is extruded. Finally, the reciprocating movement is stopped and the upset force is applied to complete the welding.