Effect of Ni on microstructure and properties of SMAW deposited metal on Q690 steel

The welding consumables of Q690 high-strength steel were taken as the research object, effects of Ni content on the microstructure and mechanical properties of deposited metal by shielded metal arc welding（SMAW） were studied by means of optical digital microscope, scanning electron microscope and fracture analysis. The results showed that the solution strengthening and fine grain strengthening were the main strengthening mechanism of deposited metals. The addition of Ni could effectively modify the microstructure and mechanical properties of the deposited metal. With the increase of Ni content, the tensile strength of the deposited metal increased while the impact performance decreased. Appropriate amount of Ni addition could cause the increase of acicular ferrite. However, excessive addition of Ni resulted in the decrease of acicular ferrite,and the formation of lath bainite and martensite, which caused the deterioration of the impact properties of the deposited metal.