Study on the Evolution Mechanism of molten pool surface morphology of Negative Pressure Arc welding via Fully Coupled Arc-Pool Free Surface Model

The accuracy of thin-walled structures in arc additive manufacturing components is limited by the overflow of molten pool caused by positive pressure arc. Therefore, our team introduced negative pressure arc additive technology, but the research on the mechanism of molten pool movement under negative pressure arc has not been explored yet. Therefore, a fully coupled arc pool model containing free surface deformation is used to study the interactions between heat, force, flow, and free surface morphology under negative pressure conditions in the melt pool. The results indicate that negative pressure arc can effectively improve the depression of the molten pool. With the increase of welding current and magnetic field strength, the electromagnetic stirring force is enhanced, and the molten pool exhibits severe centrifugal phenomenon, leading to an increase in molten pool depression. Negative pressure arc achieves a more uniform distribution of heat input, forming a low-temperature zone in the center of the melt pool. Through the Marangoni effect, a counter current zone is generated, thereby reducing the flow velocity at the center of the molten pool. This study has made significant contributions to understanding the mechanism of molten pool under negative pressure and laid a theoretical foundation for the application of negative pressure arc addition technology.

电弧增材制造构件中薄壁结构的精度受正压电弧引发的熔池溢出所限制。为此，本团队引入了负压电弧增材技术，但负压电弧作用下熔池运动机制的研究尚未深入开展。因此，本研究采用包含自由表面变形的全耦合电弧熔池模型，探究负压条件下熔池内热量、力、流动与自由表面形态之间的相互作用。研究结果表明，负压电弧可有效改善熔池凹陷；随着焊接电流与磁场强度的增大，电磁搅拌力增强，熔池出现严重的离心现象，导致熔池凹陷程度加剧。此外，负压电弧实现了更均匀的热输入分布，在熔池中心形成低温区；通过马兰戈尼效应（Marangoni effect）产生逆流区，从而降低熔池中心的流动速度。本研究为理解负压下熔池机制做出了重要贡献，也为负压电弧增材技术的应用奠定了理论基础。