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<p>Q355E high-strength structural steel is widely used in thick-plate welding applications for construction machinery. While high-heat-input metal active gas (MAG) welding enhances welding efficiency, it tends to induce coarse grain structures and degraded mechanical properties in welded joints. To date, there remains a lack of systematic research into the coupled effects of welding current on the microstructure, texture, and mechanical properties of Q355E steel under high heat input conditions. This study investigated the effects of varying welding currents on the microstructure, EBSD characteristics, texture, and mechanical properties of Q355E high-strength structural steel during MAG welding under high heat input conditions. Combined with coupled thermomechanical simulation analysis of stress-strain distribution, the research aimed to determine optimal welding parameters. Results indicated: The ferrite content within the weld joint decreased with increasing welding current; EBSD analysis revealed a disordered, interwoven network structure in the weld core zone, exhibiting high average KAM values and high dislocation density; Extensive dynamic recrystallisation occurred in both the coarse grain zone and fine grain zone of the joint, with the coarse grain zone showing the highest recrystallisation rate (74.7%); The welded joint predominantly exhibited {001}&lt;100 &gt; texture; XRD peaks were sharply defined, corresponding to the α-Fe phase, with grains oriented along the (110) direction. Simulation and experimental results jointly confirm that 500&#xa0;A represents the optimum welding current. At this parameter, the joint exhibits uniform equivalent stress distribution with a gentle gradient. Both the maximum equivalent stress and equivalent plastic strain are the lowest among all groups, yielding optimal mechanical properties: tensile strength of 496.33&#xa0;MPa and elongation of 20.4%. The fine grain zone demonstrated the highest hardness, reaching 209.81 HV.</p>

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Effect of welding current on the microstructure and mechanical properties of Q355E steel welded joints under high-heat-input MAG welding

  • 期刊论文

  • 发表日期：

    2026年4月29日

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  • Yuhao Wang,
  • Youping Sun,
  • Yuwei Lu,
  • Jiangmei He,
  • Wangzhen Li

摘要

Q355E high-strength structural steel is widely used in thick-plate welding applications for construction machinery. While high-heat-input metal active gas (MAG) welding enhances welding efficiency, it tends to induce coarse grain structures and degraded mechanical properties in welded joints. To date, there remains a lack of systematic research into the coupled effects of welding current on the microstructure, texture, and mechanical properties of Q355E steel under high heat input conditions. This study investigated the effects of varying welding currents on the microstructure, EBSD characteristics, texture, and mechanical properties of Q355E high-strength structural steel during MAG welding under high heat input conditions. Combined with coupled thermomechanical simulation analysis of stress-strain distribution, the research aimed to determine optimal welding parameters. Results indicated: The ferrite content within the weld joint decreased with increasing welding current; EBSD analysis revealed a disordered, interwoven network structure in the weld core zone, exhibiting high average KAM values and high dislocation density; Extensive dynamic recrystallisation occurred in both the coarse grain zone and fine grain zone of the joint, with the coarse grain zone showing the highest recrystallisation rate (74.7%); The welded joint predominantly exhibited {001}<100 > texture; XRD peaks were sharply defined, corresponding to the α-Fe phase, with grains oriented along the (110) direction. Simulation and experimental results jointly confirm that 500 A represents the optimum welding current. At this parameter, the joint exhibits uniform equivalent stress distribution with a gentle gradient. Both the maximum equivalent stress and equivalent plastic strain are the lowest among all groups, yielding optimal mechanical properties: tensile strength of 496.33 MPa and elongation of 20.4%. The fine grain zone demonstrated the highest hardness, reaching 209.81 HV.