Underwater friction taper plug welding process and mechanical properties of joints for DH36 steel

The present study focus on exploring the underwater friction taper plug welding process and the joints mechanical properties for DH36 steel. The results indicate that at lower rotating speed, lack of bonding defect would form in the weld. Increasing the rotating speed is helpful for improving the weld quality and avoiding the formation of weld defects. In such situation, proper welding parameters are recommended as the rotating speed of 7 500 rpm and axial force ranging from 30 to 45 kN. The microstructure in the weld zone is consist of bainite and martensite, and in HAZ is mainly of bainite. Both tensile and impact properties could be improved by increasing the rotating speed, however, no significant variation can be found by changing the axial force. Under proper welding parameters (7 500 rpm rotating speed and 40 kN axial force) the weld would have excellent mechanical properties of 370 MPa yield strength, 530 MPa ultimate tensile strength, 22.5% elongation and 42.5 impact toughness at 0 ℃.