主辅丝协同控制的单电弧窄间隙焊接方法及机理

To effectively solve the mutual restriction problem of welding quality and efficiency in current single-arc narrow gap processes, this project proposes a new process of single-arc narrow gap welding controlled cooperatively by main and additional wires. This process increases the deposition rate of single-arc narrow gap welding by using arc heat and molten metal heat to melt additional wire at the same welding input, while making the swing arc on main wire end to promote groove sidewall penetration. Simultaneously, the additional wire is cooperatively weaved at the same direction and frequency as those of the arc according to the position of arc swing, and the feeding rate of additional wire into the arc is controlled synchronically with the position of additional wire in groove, so that regulating the heat-absorbing distribution of additional wire and thus improving weld formation quality. This research will be focused on the heating and melting characteristics of additional wire, and the process effects and their characterization of additional wire during arc swinging. In addition, it will investigate the cathode spots behaviors of the arc, the characteristics of droplet transfer, the flowing phenomena of molten metal, the change of welding temperature field, the laws of weld solidification and formation, and the microstructure features of welding joint in the presence of additional wire. Finally, the methods and effects of cooperative controls between the main and additional wires, and the increasing mechanism of both joint quality and welding efficiency will be revealed. The above work will aid to establish the theoretical fundamentals of single-arc narrow gap GMA welding under the cooperative controls, and to promote the developments in the theory and technology of high efficiency and automatic welding.

针对单电弧窄间隙焊接质量与效率相互制约的问题，本项目提出一种主辅丝协同控制的单电弧窄间隙焊接方法，在发挥主丝摇动电弧促进坡口侧壁熔深形成作用的同时，通过在相同焊接线能量下利用电弧热和熔池液态金属热熔化辅丝，提高单电弧窄间隙焊接熔敷速度，并根据电弧摇动的位置信息，使辅丝作与电弧摇动同向和同频率的协同摆动，根据辅丝在焊接坡口内位置变化，对辅丝送进速度进行协同控制，以调节辅丝吸热分布、改善窄间隙焊缝成形质量。着重研究摇动电弧下辅丝加热熔化特性、辅丝工艺效应及其表征，研究辅丝作用下电弧阴极斑点行为、熔滴过渡特性、熔池流动现象、焊接温度场变化、焊缝凝固成形规律、接头组织特征，研究主辅丝综合协同控制方法及效应、以及接头性能与焊接效率协同提升机制，建立主辅丝协同控制下单电弧窄间隙GMA焊接的理论基础，促进高效化及自动化焊接理论与技术的发展。

针对单丝电弧窄间隙焊缝成形质量不高和焊接效率较低的问题，本项目提出了主辅丝协同的摇动电弧窄间隙焊接方法及数字化控制系统，通过添加辅丝显著提高了窄间隙焊接效率，通过辅丝摆动及加热调节了辅丝吸热分布和热丝摇动电弧线能量分布、明显改善了窄间隙焊缝成形。研究了主辅丝协同控制方法、辅丝熔化特性，研究了辅丝作用下摇动电弧行为、熔滴过渡特性、焊接温度场变化、焊缝成形机理、接头组织特征，建立了坡口状态参数精确检测方法，提出了通过焊接熔敷速率和焊缝层数减少率的窄间隙焊接效率综合评价方法，分析了热丝作用下摇动电弧前后摆动行为、电弧线能量分布，阐明了辅丝工艺效应、焊缝成形规律、焊接质量效率协同提升机制，建立了单电弧双丝窄间隙焊接的理论及技术基础。.研究结果表明，增大辅丝送进速度时，辅丝金属过渡方式从滴状过渡、搭桥过渡、转变为熔入式过渡；辅丝与熔池接触时，电弧阴极斑点部分地向辅丝转移，促进了辅丝熔化，并抑制了电弧沿坡口侧壁攀爬、主辅丝之间主丝熔滴串行短路、主丝熔滴旋转射流过渡，提高了电弧稳定性。增大辅丝摆幅时，辅丝在坡口内吸热分布趋于均匀；增大热丝电流时，在热丝磁场洛伦兹力和电弧自身电磁力作用下，加快了电弧相对主丝的前后摆动，明显减小了电弧线能量。添加辅丝细丝焊时，增大辅丝摆幅、热丝电流、辅丝送进速度，坡口侧壁熔深和焊缝最大厚度基本不变，焊缝底部熔深减小，焊缝底部双峰显著改善；冷丝辅助粗丝焊时，焊缝底部成形无双峰现象。在获得良好窄间隙焊缝成形的同时，与单丝焊相比，冷丝辅助细丝焊接熔敷速率提高了约57%、焊缝层数减少了约36%，热丝辅助细丝焊接熔敷速率提高了约49%、焊缝层数减少了约33%，其焊接熔敷速率与冷丝辅助粗丝焊时相当。