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<p>Self-shielded flux core arc welding (FCAW-S) can be applied in underwater maintenance and repair operations. However, this process presents poor arc stability and bubble generation in the weld puddle, negatively affecting mechanical properties. This research analyzed the structural characteristics of the fusion zone (FZ) in an A36 steel plate welded by FCAW-S, and their relationship with the process parameters. A central composite design of experiments (DOE) was proposed with 24&#xa0;V and wire feed speed (WFS) of 148.16&#xa0;mm/s as constant values. As variables, the contact tip to work distance (CTWD) was set between 4 and 10&#xa0;mm with a welding speed (WS) between 2 and 3.4&#xa0;mm/s using a commercial wire E71T-GS of 0.9&#xa0;mm. The surface of the welds showed the characteristic asymmetrical appearance and 2 to 5% internal porosity percentages. Heat input (<i>Q</i>) was calculated using amperage (A), voltage (V), and WS; at <i>Q</i> = 1510&#xa0;J/mm, the microstructure was completely martensitic; at <i>Q</i> = 1906&#xa0;J/mm, the microstructure was martensitic with large regions of bainite, and cracks generated by microporosities. The highest <i>Q</i> = 2372&#xa0;J/mm presented a microstructure with acicular ferrite (AF) nucleating from non-metallic inclusions, considerably reducing the FZ Vickers microhardness up to 278 HV<sub>0.5</sub>. The slight variation in welding parameters affects the geometrical response of the welds. The weld quality can be improved using a good combination of parameters. Still, the internal porosity did not have a linear relationship with <i>Q</i> due to the dissociation of the water molecule and the interaction of hydrogen and oxygen in molten metal.</p>

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Underwater welding: Evaluation of the structural characteristics of the fusion zone generated in an A36 structural steel welded by FCAW-S

  • 期刊论文

  • 发表日期：

    2025年4月3日

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  • Luis A. Guía-Hernández,
  • Rocío M. Ochoa-Palacios,
  • Patricia S. Costa,
  • Gerardo Altamirano-Guerrero,
  • Perla J. Reséndiz-Hernández,
  • César A. Facusseh-Valerio

摘要

Self-shielded flux core arc welding (FCAW-S) can be applied in underwater maintenance and repair operations. However, this process presents poor arc stability and bubble generation in the weld puddle, negatively affecting mechanical properties. This research analyzed the structural characteristics of the fusion zone (FZ) in an A36 steel plate welded by FCAW-S, and their relationship with the process parameters. A central composite design of experiments (DOE) was proposed with 24 V and wire feed speed (WFS) of 148.16 mm/s as constant values. As variables, the contact tip to work distance (CTWD) was set between 4 and 10 mm with a welding speed (WS) between 2 and 3.4 mm/s using a commercial wire E71T-GS of 0.9 mm. The surface of the welds showed the characteristic asymmetrical appearance and 2 to 5% internal porosity percentages. Heat input (Q) was calculated using amperage (A), voltage (V), and WS; at Q = 1510 J/mm, the microstructure was completely martensitic; at Q = 1906 J/mm, the microstructure was martensitic with large regions of bainite, and cracks generated by microporosities. The highest Q = 2372 J/mm presented a microstructure with acicular ferrite (AF) nucleating from non-metallic inclusions, considerably reducing the FZ Vickers microhardness up to 278 HV0.5. The slight variation in welding parameters affects the geometrical response of the welds. The weld quality can be improved using a good combination of parameters. Still, the internal porosity did not have a linear relationship with Q due to the dissociation of the water molecule and the interaction of hydrogen and oxygen in molten metal.