短路电弧熔滴过渡的多脉冲同步磁场控制研究

CO_2 short-circuiting welding is a very important welding method, which is the most widely used in industry. The inherent defects of the extensive spatters and imperfect bead formation restrict it not to be used in an intermediate welding condition. Many scholars have been seeking a way to provide a basis for the current control of liquid bridge all the time, but it is very difficult to sense the information about liquid bridge accurately and quickly. The main reason is that liquid bridge shrinkage needs a higher current, but reducing spatters needs a lower current, and this is a contradiction, which is not solved completely. It is even out of control in a greater current in CO_2 short circuit transfer. Therefore, a new method of multipulse synchronous magnetic field control is put forward in this project, which will meet the requirements of different current and electromagnetic force in each period of short circuit transfer, through the synchronous control of multiple current pulses and magnetic pulses, especially adding a low frequency magnetic pulse in arc phrase and applying a high frequency and high intensity magnetic pulse in liquid bridge shrinkage phrase before detachment of droplet. The arc will expand in a low frequency magnetic field and will be compressed in a high frequency magnetic field in terms of preliminary scentific work, which are just what the arcing phase and liquid bridge phase of CO_2 short cirrcuit welding need correspondingly. That is to say, the arc expansion will facilitate arc spot to move up and decrease spot pressure not to block droplet transfer, and the electromagnetic force, which is generated by adding many current impulses and magnetic pulses in each period of short circuit transfer, especially applying a high frequency and high intensity magnetic pulse at the time of liquid bridge separation, will facilitate the droplet to transfer steadily with the surface tension together. Based on the arc physics, welding Metallurgy and electromagnetic theory, this project will try to reveal the mechanism of ″electro-magnetic″ mutual coupling and interaction between pulse fields and metal transfers through measuring the arc characteristics and analyzing the forces on a droplet. It is hopeful to provide a new way or a new method, which may embody the features of superior quality, high efficiency and low cost for pure CO_2 short circuit transfer welding used in an intermediate welding condition to a great extent. It will still supply a reference for other metal transfer control.

短路过渡CO_2焊是一种重要方法，应用量大而面广。因存在飞溅大、成形差等固有缺点，限制了在中等规范中应用。一直以来，许多学者都在探寻一种方法为液桥电流控制提供依据，但准确和快速检测液桥信息尚存在很大难度，主要原因是短路过渡存在着一对矛盾即液桥收缩需要大电流，而减少飞溅需要小电流，且在较大电流时出现失控，此问题始终未根本解决。为此，本项目提出一种多脉冲同步磁场控制方法，通过多个电流脉冲和磁脉冲的同步控制，尤其在燃弧期施加低频磁脉冲，液桥爆断时加入高强磁脉冲，来满足短路过渡不同阶段不同电流大小和电磁力的需要。本项目拟以电弧物理、焊接冶金、电磁理论为基础，通过测试分析电弧特性及熔滴受力情况，揭示"电、磁"互相耦合机制以及脉冲磁场对熔滴过渡作用机理，课题研究有望为中等规范CO_2焊短路过渡控制提供一种新的途径和方法，在更大程度上体现其优质、高效、低成本特点，对其他熔滴过渡控制也将带来一种借鉴。

在国家自然科学基金的资助下，按照4年计划进度进行了磁控CO2励磁电源样机研制和大量的磁控短路电弧熔滴过渡焊工艺研究工作，取得了预期效果。项目研制了三套磁控耦合电源（双逆变小电流低频励磁电源、基于单片机控制双逆变大电流中频励磁电源以及基于DSP+ARM控制的大电流高低频磁耦合电源）。基于DSP+ARM控制的大电流高低频磁耦合电源主回路采用高频率IGBT软开关逆变技术，实现快速响应。由于电弧短路发生时间仅为十几微秒，因此主控板采用处理速度高达600MHz的DSP和实时性强的ARM组成双CPU控制系统，实时监测电弧状态并进行有效的精细控制。实现了磁控CO2焊短路电弧熔滴过渡的同步磁场控制。开发了一种低飞溅磁控CO2焊接电源。利用研制的磁耦合电源，拍摄电弧形态、测试磁控电弧特性，对熔滴过渡各阶段受力情况进行计算和分析，建立熔滴受力数学表达式；开展了磁场对焊缝成形影响规律实验、磁场对焊接飞溅率测定实验，数值模拟电弧温度分布，理论分析磁控短路电弧熔滴过渡各阶段不同变化，建立了磁控电弧数学模型。深入研究了同步脉冲磁场在熔滴过渡的燃弧阶段、短路阶段以及液桥阶段，电磁力对电弧旋转半径、熔滴过渡频率、熔滴尺寸大小、过渡飞溅率以及焊缝成形的影响机理。最后实际施焊的结果表明，同步磁控脉冲CO2焊在飞溅及焊缝成形方面获得明显改善，为高效CO2磁控焊接工艺的发展和应用提供了理论和实验基础，对其他熔滴过渡方式的同步磁场控制也将带来一种借鉴价值。课题研究成果申请中国发明专利3项，其中1项发明专利获得授权，发表论文12篇，其中SCI收录3篇、EI收录4篇；提交博士学位论文1篇，硕士学位论文8篇。主编著作1部，课题部分研究成果获得辽宁省科技进步二等奖1项。