氧作用下高速TIG焊耦合电弧/熔池界面行为及其焊缝成形机理

In present project, coupled arc is employed together with oxygen introduced as activating element to control the interface of arc plasma and weld pool. As a result, undercut and humping defects generated in high current TIG welding with high speed can be eliminated significantly. In addition, an increased weld penetration is obtained with good mechanical property and thus can become a high efficient welding process with low cost. For all this, following critical issues is going to be studied further: a model is to be developed of oxygen transfer across the interface of coupled arc and weld pool and the oxygen transfer from the arc plasma to the weld pool is to be researched, so that the oxygen transfer can be formulated quantitatively; on the basis of experiment, an integrated mathematical model of coupled arc and weld pool is established to investigate the interface behavior and interaction mechanisms of the coupled arc and weld pool; following this, mechanisms of weld pool flow driven and suppression of undercut and humping to be examined as well as the relationship of process parameter, weld formation, welding joint and mechanical property is to be established, the mechanisms of weld bead formation and regulation of high speed welding with combination of oxygen and coupled arc is clarified accordingly. This study of the project are of great significances in understanding interaction and interface of arc and weld pool to restrain welding defect and thus promote the development and application of high efficiency welding manufacturing with high quality and low cost.

本项目提出一种采用活性元素氧改变耦合电弧/熔池界面行为的方法，可以明显抑制大电流高速TIG焊的咬边和驼峰缺陷，同时增加熔深并保证焊接接头力学性能，有望成为一种新型的高效低成本焊接方法。为此，将对以下问题展开深入研究：建立活性元素氧在耦合电弧/熔池界面的传输模型，研究氧从电弧气氛到熔池的传输行为，实现对氧传输过程的定量描述；建立耦合电弧-熔池一体化数学模型，结合实验研究，研究氧作用下的耦合电弧/熔池界面行为和交互作用机理；在此基础上，探讨高速焊熔池流动驱动机制与咬边和驼峰焊道抑制机理，建立工艺参数与焊缝成形、接头组织和力学性能之间的相关关系，揭示氧与耦合电弧联合作用下高速焊焊缝成形与改善机理。本项目的研究对于深入认识电弧/熔池界面行为和抑制焊接缺陷，推动高效优质低成本焊接制造的发展和应用具有重要意义。

随着全球能源危机和环境问题的日益严重，高效、绿色、优质和节能的生产过程成为制造业发展的必然趋势，这也对焊接制造提出了更高的要求。基于此，本项目对一种采用活性元素氧改变耦合电弧/熔池界面行为的高效焊接方法，可以明显抑制大电流高速TIG焊的咬边和驼峰缺陷，同时增加熔深并保证焊接接头力学性能。针对这一方法，本项目深入研究了活性元素氧在耦合电弧/熔池界面的传输过程、氧作用下的耦合电弧/熔池界面行为和交互作用机理，以及高速焊熔池流动驱动机制与咬边和驼峰焊道抑制机理。结果表明：①氧在电弧气氛中和熔池附近均呈现明显的非均匀分布，意味着熔池表面吸附的氧浓度也不均匀；耦合电弧电流的大小和钨极电流的分配对氧的传质过程有显著的影响，影响氧非均匀分布的内在机理是温度梯度、浓度梯度和对流三者作用下传质效果的相对强弱。②原子氧对熔池中氧浓度有明显的强化作用，以及氧在熔池表面的溶解随温度的升高而降低。③大电流TIG焊接时出现咬边和驼峰缺陷是由大电流下的电弧压力和等离子流剪切力两者的共同作用导致的，前者造成明显的熔池下凹和略高于熔点的熔池温度，后者导致熔池较明显的下凹变形和金属向尾部强烈的流动，而表面张力、电磁力和浮力对熔池流动的驱动作用很弱。④耦合电弧的电弧压力和等离子流剪切力显著下降，成为消除驼峰缺陷的主要因素，表面张力再次成为熔池流动的主要驱动力，增加了焊缝熔深；同时，由于活性元素的作用，三相界面中的电弧/熔池界面张力降低，咬边缺陷进一步被抑制，实现了大电流条件下的高效深熔焊接。本项目的研究进一步深化了对活性气体在电弧-熔池系统的传质过程和机理的认识，同时也使人们对高速焊焊缝成形和抑制机理的理解更加深入，对于更有效的利用混合气体电弧和促进高效、优质和低成本的焊接制造的发展具有重要意义。