Effect of Ni on microstructure and mechanical properties of underwater wet welding joint

• Over 30% acicular ferrite is obtained in weld metal with Ni content of 2.04–2.45 wt.%.
• Martensite and martensite–austenite component increase in weld with higher Ni content.
• The tensile strength increases with the increasing of Ni content between 0 and 3.16 wt.%.
• Highest impact toughness of weld metal is obtained with Ni content of 2.45 wt.%.

Underwater wet welding was performed in the present work, and different Ni contents from 0.19 to 5.18 wt.% in underwater weld metal are obtained by the addition of Ni into the covering of electrodes. The joints are welded in fresh water by welding diver in the experimental pool with the water depth of 3 m, and then analyzed by OM, XRF, SEM and EDS. The emphasis is placed on studying the effect of the Ni content on the variation regulation of the microstructure, tensile strength and low-temperature toughness of the underwater wet welding joint. Base on the experimental results, the relation of Ni content and the joint quality of underwater wet welding is established, and the optimal Ni content is determined.

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