高频磁约束TIG焊电弧行为研究

A new method of the high frequency magnetized TIG arc welding is put forward from an innovative angle. The conventional TIG arc welding has defects of heat decentralization and low efficiency which will be solved by this new method effectively. The welding arcs under an external high-frequency magnetic field have unique characters and different behaviors compared with the conventional TIG arcs. For example, with the low frequency magnetic field, the distribution of arc pressure (including arc current density etc.) forms an annular bimodal peak. When adding a high frequency of the external magnetic field, the annular bimodal distribution begins to disappear unusually. Meanwhile, the arc pressure, energy density, and penetration of weld bead increase evidently, according to our preliminary experimental results. High frequency magnetized TIG shows the effect of magnetic confinement and potential applications in industry due to the high efficiency. But the mechanism of the behavior of arcs under high frequency magnetic field is still unclear and unrevealed. Therefore, based on the hydrodynamics and kinetic theory, the phenomena and mechanism of the interaction between the arcs and the electromagnetic fields with large range of the magnetic field parameters will be investigated systematically, through the experiments, the theoretical analysis, and the numerical simulation. The purpose is to develop a completed theory on the behaviors of magnetically controlled TIG welding arc and to realize the simulation program according to the theory. This project will focus on the exploration of the theoretical foundation for the arc physics to understand and predict the nature of magnetized TIG and try to reveal the mechanism of high frequency magnetic confinement. It is hopeful to provide a new way or an innovative method, which may embody the features of superior quality and low cost for high performance TIG arc welding to a great extent.

本项目将从一种新的角度展开对TIG焊的创新研究，提出一种高频磁约束TIG焊方法，以解决其电弧热量分散和效率低问题。高频磁约束电弧特性将表现出与传统电弧或低频磁控电弧不一样的行为，如低频或直流磁场作用下形成的电弧压力（密度）呈环形双峰分布，在高频磁场作用下却奇异消失，电弧压力、能量密度和焊缝熔深比传统电弧明显提高（本项目前期试验结果）。高频磁约束电弧表现出磁压缩效应及潜在应用前景，但这种电弧行为变化机理尚未明晰。为此，本项目拟以磁流体力学理论和动理学理论为基础，通过实验、理论分析与数值模拟等手段，系统研究焊接电弧与大范围内变化的电磁场之间相互作用的机理与规律，构建一套系统描述磁控焊接电弧行为的理论及模拟仿真程序。本项目研究将为更加全面了解并预测电弧物理本质及其运动的全过程奠定理论基础，并有望为高效化TIG焊创新发展开辟一种新的途径和方法，在更大程度上体现TIG焊优质和低成本特点。

在国家自然科学基金的资助下，按照4年计划进度进行了高频磁约束TIG焊电弧行为研究，研制了高频电磁脉冲TIG电源，开展了大量磁控TIG焊接工艺试验研究和磁场与电弧相互作用机制等基础研究工作，取得了预期效果。项目研制了中小等功率MCWE-40/2000和大功率（基于DSP+ARM 控制系统）两种励磁电源，设计研制了新型多功能磁头，可实现纵向、横向、尖角磁场等，研制了一种高频电磁脉冲高性能TIG焊接电源。研究了磁场及其分布与电弧形态之间的关系，纵向磁场和尖角磁场的模拟结果与实验基本吻合；研究了电弧运动过程，分析了纵向磁场和尖角磁场作用下电弧受力与形态变化情况；测试了电弧压力分布，建立了外加磁场作用下电弧压力分布模型。对电弧中心热量测量结果显示：电弧中心的温度与电弧中心压力分布相似，也是随励磁频率高，电弧温度先下降再上升，到1500Hz时达到最高；通过测试焊缝熔深熔宽，结果表明，焊缝成形系数在1500Hz时达到最大。揭示了电弧的导电机构以及电弧中带电粒子运动机制与电弧压缩机理：高频磁场的引入，改变了电弧导电机构的分布，使电弧三个区：电离区、复合区和能跃区的尺寸发生变化；同时改变了各区带电粒子的浓度和运动速度。随励磁频率的增加，带电粒子在两条螺旋线间跳跃的距离减小，使电弧三个区的径向尺寸减小，表现为电弧的收缩。研究成果在矿物绝缘防火电缆制管工艺以及焊管工艺获得应用，提高薄壁焊管的焊接速度(由传统 TIG 焊接速度 0.5m/min 提高到 5.0m/min)，防火电缆制管生产效率提高 2-3 倍。项目研究为高效高性能TIG电弧焊提供了理论和实验基础，对其他电弧等离子体热源调控也将带来一种借鉴价值。课题研究成果申请中国发明专利4项，实用新型专利4项，其中2项实用新型专利获得授权；发表论文10篇，发表会议论文5篇，其中SCI收录3篇、EI收录2篇；提交硕士学位论文8篇；参与编著1部。