步进填丝双脉冲TIG电弧增材精确成形方法及调控机理

Metal filler-based wire and arc additive manufacturing (WAAM) is the most efficient and economical way to realize the near net shape forming for the large complex components. How to assure the hyper-stability in the wire and arc additive forming process and precisely control its forming dimensions are the key issues. To resolve above problems, a new additive manufacturing method named double-pulse TIG with stepped filling wire is proposed in this proposal, and the coupling action of heat and mass transfer in the arc-droplet system is decoupled. On this basis, taking the dynamical evolution of weld pool as the research topic and the stability control of weld pool system as the research target, the following key scientific problems will be studied in this program: (1) the self-stabilizing mechanism of arc-droplet-weld pool system in the additive manufacturing process by means of point-by-point and layer-by-layer deposition; (2) the thermal compensation mechanism of forming the optimal characteristics of weld pool affected by heat accumulation. (3) the internal influence rule and mechanism between the weld pool flow state and the surface morphology in deposition layers. Further, based on that, the control method and scientific evolution theory system of precision forming additively fabricated by double-pulse TIG with stepped filling wire will be established. The studied results will provide a theoretical support to realize the precise control of WAAM formation and have a significant academic value to enrich and develop that basic theories.

金属丝材电弧增材制造工艺是实现大型复杂构件增材近净成形最高效经济的手段，如何保证电弧增材成形过程的超稳定并精确控制成形精度是其核心问题。针对以上问题，本项目提出步进填丝双脉冲TIG电弧增材制造新方法，实现电弧-熔滴系统的热-质传输解耦。在此基础上，以熔池动态演化过程为研究对象，以控制熔池系统稳定性为目标，对以下关键科学问题进行研究：①逐点逐层熔积过程中电弧-熔滴-熔池系统的自稳定性机制；②热沉积作用下形成最优熔池特征的热补偿机制；③熔池流态与熔积层表面形貌的内在影响规律和机理；并以此进一步建立步进填丝双脉冲TIG电弧增材精确成形的调控方法和科学理论评价体系，为实现步进填丝双脉冲TIG电弧增材成形的精确控制提供理论支撑，对丰富和发展电弧增材成形精确控制基础理论具有重要的学术研究价值。

针对如何保证电弧增材成形过程的超稳定并精确控制成形精度这一关键共性问题，本项目创新性地提出了步进填丝双脉冲TIG电弧增材制造方法，并以增材熔池动态演化过程为研究对象，以控制熔池系统稳定性为目标，重点开展了以下研究：（1）DP-TIG增材制造试验系统设计与软硬件集成实现；（2）步进填丝双脉冲TIG电弧增材制造工艺试验研究，包括双脉冲电流对熔池动态行为调控，DP-TIG增材电弧-熔滴-熔池行为，沉积工艺参数对增材过程稳定性和成形形貌的影响规律；（3）DP-TIG增材热-质传输过程数学建模与模拟仿真，包括焊丝熔化与熔滴过渡的数学物理模型，送丝速度、送丝角度、高脉冲电流群参数和沉积速度对熔滴过渡行为的影响仿真；（4）熔池热补偿稳定性调节与增材成形精度控制，包括熔池失稳理论分析，熔池热-力平衡数学模型，基于数学模型参考预测和在线调控沉积速度补偿熔池热输入的动态控制增材成形精度的策略，相关验证性试验。研究结果表明，双脉冲电流波形配合步进送丝能够实现TIG增材过程中热质传输的独立控制，双脉冲电流对熔池几何尺寸和形貌具有良好的调控作用；熔滴以液桥过渡方式熔入到熔池更能提高成形精度；后送丝下熔滴过渡频率增加、尺寸更小，成形精度更高；调节高脉冲电流群参数、送丝角度、沉积速度时，熔滴过渡位置均在0.5mm~1.9mm变化，成形过程稳定；基于热积累补偿熔池热输入策略增材可有效降低热积累，使成形件成形精度明显得到改善；相比调节低脉冲群电流，调节沉积速度时增材过程更稳定，成形件宽度和高度尺寸更均匀，波动更小。项目研究理论成果为电弧增材技术在高效高精度一体化成形大尺寸复杂构件领域中的工程化应用提供了有力的理论支撑，所形成的关键技术有望应用于国防军工武器装备装甲车辆关键部件（如坦克传动齿等）的野外电弧增材现场快速制造和修复，对野外战场环境下维持和提升军队战斗力、打赢信息化现代战争具有重要的国防意义。