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<p>Laminar plasma arc, a novel welding heat source, exhibits reduced stability with longer arc lengths. To broaden its applications, this study used longitudinal magnetic fields to constrain arc behavior, examining DC and AC effects, and then selected AC fields for thick-plate narrow gap welding with microstructure and performance tested. Results show that increasing DC magnetic field intensity causes arc deviation from the axis and instability, and longer arc lengths narrow the adjustable magnetic field range: arcs start to deviate at 16 mT, 14 mT, and 12 mT for 16 mm, 21 mm, and 26 mm arc lengths, respectively. Higher intensity increases the arc bottom dimension Dp: for 16 mm arcs, DC (8–18 mT) raises Dp from 12.78 to 15.08 mm, AC (2–6 mT) from 12.38 to 12.8 mm; increasing frequency (40–200 Hz) reduces Dp to 12.03 mm via intensified particle collisions. AC fields better regulate narrow gap bottom coverage: under 8–14 mT DC, the arc coverage width increases by only 0.6 mm, while under 2–6 mT AC, the increase reaches 4.14 mm. Magnetic field fragment dendrites via stirring, weakening weld structure directionality, enhancing deformation resistance, promoting high-hardness ferrite, and boosting microhardness. Magnetic field intensity significantly affects sidewall penetration, tensile strength, and elongation: at 6 mT/80 Hz, these reach 1.83 mm, 698.77 MPa, 32.6% (increasing by 36.6%, 6.7%, 114.5% compared with the no-field condition, respectively). Magnetic field frequency improves cross-sectional consistency. This study provides theoretical and practical guidance for expanding long arc laminar plasma arc application in thick-plate narrow gap welding via magnetic field control.</p>

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Magnetic control of laminar plasma arc: arc behavior and narrow gap welding

  • 期刊论文

  • 发表日期：

    2025年10月3日

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  • Honglei Zhao,
  • Siyu Zhang,
  • Hao Chen,
  • Yiwen Li,
  • Junyan Miao,
  • Zhihai Dong,
  • Yunlong Chang

摘要

Laminar plasma arc, a novel welding heat source, exhibits reduced stability with longer arc lengths. To broaden its applications, this study used longitudinal magnetic fields to constrain arc behavior, examining DC and AC effects, and then selected AC fields for thick-plate narrow gap welding with microstructure and performance tested. Results show that increasing DC magnetic field intensity causes arc deviation from the axis and instability, and longer arc lengths narrow the adjustable magnetic field range: arcs start to deviate at 16 mT, 14 mT, and 12 mT for 16 mm, 21 mm, and 26 mm arc lengths, respectively. Higher intensity increases the arc bottom dimension Dp: for 16 mm arcs, DC (8–18 mT) raises Dp from 12.78 to 15.08 mm, AC (2–6 mT) from 12.38 to 12.8 mm; increasing frequency (40–200 Hz) reduces Dp to 12.03 mm via intensified particle collisions. AC fields better regulate narrow gap bottom coverage: under 8–14 mT DC, the arc coverage width increases by only 0.6 mm, while under 2–6 mT AC, the increase reaches 4.14 mm. Magnetic field fragment dendrites via stirring, weakening weld structure directionality, enhancing deformation resistance, promoting high-hardness ferrite, and boosting microhardness. Magnetic field intensity significantly affects sidewall penetration, tensile strength, and elongation: at 6 mT/80 Hz, these reach 1.83 mm, 698.77 MPa, 32.6% (increasing by 36.6%, 6.7%, 114.5% compared with the no-field condition, respectively). Magnetic field frequency improves cross-sectional consistency. This study provides theoretical and practical guidance for expanding long arc laminar plasma arc application in thick-plate narrow gap welding via magnetic field control.