Abstract
Abstract The paper described the experimental findings of underwater wet welding of E40 steel using self-shielded flux-cored wire with a TiO2-FeO-MnO slag system. The arc stability, weld quality and corrosion resistance with different heat inputs were studied. The results showed that the wet welding process of the designed wire displayed good operability in the range of investigated parameters. The microstructure and mechanical properties of the weld metal depended on the heat input. Due to the high fraction of acicular ferrite in the weld metal, the mechanical properties of the weld metal under low heat input had better tensile strength and impact toughness. Fracture morphologies at low heat input had uniform and small dimples, which exhibited a ductile characteristic. The diffusible hydrogen content in the deposited metal obtained at a heat input of 26 kJ/cm significantly reduced to 14.6 ml/100g due to the combined effects of Fe2O3 addition and the slow solidification rate of molten metal. The microstructure also had a significant effect on the corrosion resistance of the weld metal. The weld metal with high proportions of acicular ferrite at low heat input exhibited the lowest corrosion rate, while the base metal possessed a reduced corrosion resistance. These results were helpful to promote the application of low alloy high strength steel in the marine fields.
Highlights
Underwater wet welding, a convenient and low-cost technique, is widely used in the maintenance and repair of underwater steel structures [1]
The microstructure had a significant effect on the corrosion resistance of the weld metal
The corrosion resistance of the base metal and weld metal was evaluated by potentiodynamic polarisation (PDP) tests
Summary
Underwater wet welding, a convenient and low-cost technique, is widely used in the maintenance and repair of underwater steel structures [1]. The research on underwater wet SMAW using coated electrodes is well documented [3,4]. With the trend of the developing wet welding process with its advantages of high efficiency and a high degree of automation, the underwater FCAW-S process is receiving more and more attention [5]. Scholars around the world have conducted in-depth research on the stability of the underwater wet FCAW-S process and clearly clarified the characteristics of the bubble and droplet transfer of the underwater wet welding process [6,7,8,9]. A series of assisting methods have been proposed to achieve highquality welded joints, such as ultrasonic [10,11], pulse current [12], pulsed wire feed [13] and temper bead [14]
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