Study on microstructure and properties of 590 MPa class welding wire deposited metal on hull

By means of metallographic microscope (OM), scanning electron microscope (SEM), back scattering electron diffraction (EBSD) and transmission electron microscope (TEM), the effect of Cu on microstructure transformation and mechanical properties of deposited metal of 590MPa class steel welding wire was studied. The results show that the microstructure of deposited metal is composed of acicular ferrite, lamellar bainite, granular bainite and residual austenite. With the increase of Cu content, the phase transition temperature of the deposited metal decreases, making the phase transition region of ferrite and pearlite shift to the right, expanding the phase transition region of bainite and shrinking the phase transition region of ferrite and pearlite. The microstructure of deposited metal changed, the content of M-A elements increased but the size decreased, and the ferrite-bainite biphasic microstructure was matched. The reduction of M-A component content in strips and blocks and the reduction of effective grain size will reduce the nucleation probability of microcracks, increase crack growth resistance, and improve the impact toughness of the deposited metal.