Study of surface porosity of underwater wet welding employing FCAW-S process in structural steels

One of the main problems in using the flux-cored arc welding (FCAW) process in underwater conditions is the adequate control of the welding parameters that determine the stability of the arc and quality of the joints obtained. Thereby, the objective of this research work is to evaluate the superficial porosity variation in welding bead made on ASTM A36 steel plates using the underwater wet welding FCAW-S process. Commercial wire (AWS E71T-GS) was used to perform wet welds in simulated conditions of laboratory in a container with 30 cm of fresh water column. The configuration of the experimental tests was carried out using a central composite design and response surface methodology (RSM) analysis, obtaining an experimental matrix of 17 underwater wet welding tests. The input parameters and variation levels included wire feed speed (250-450 ipm), arc voltage (22-26 V) and welding speed (3-10 mm/s), whilst the superficial porosity was selected as the output variable of the RSM. All the samples presenting superficial porosity derived the difficulty in controlling the stability of the arc in a wet environment. From the results obtained it was possible to establish an empirical mathematical model for superficial porosity as a function of welding parameters in underwater wet welding performed with FCAW-S process. In general, it was observed that the highest porosity occurs for high values of voltage and welding speeds. The lowest levels to superficial porosity were obtained with the following parameters setting: welding speed at 3.0 to 4.4 mm/s, arc voltage at 23 to 25 V and wire feed speed between 350 and 400 ipm.