Dynamic keyhole behaviors and element mixing in paraxial hybrid plasma-MIG welding with a gap

A paraxial hybrid plasma-MIG welding process is developed to join middle-thick high strength steel plates with a butting gap. The arc and metal vapor characteristics are investigated by an advanced three-dimensional spectroscope measurement system. The dynamic keyhole behaviors and element mixing are studied by a three-dimensional numerical model. The numerical and experimental results show that the Fe vapor ejected from the wire surface, other than the plasma keyhole, has a great influence on arc char-acteristics. The butting gap affects the keyhole stability and molten metal flow, as well as the element mixing. With a gap, the keyhole opens and closes periodically. The opposing flows at the front and rear keyhole bottom walls, and the pressure imbalance in the keyhole bottom contribute to the keyhole col-lapse. The gap promotes the downward flow below the MIG arc center, which helps to transport the Ni element from the top surface of the MIG pool region to the bottom. The Pull-Push molten metal flows in the top molten pool suppress the Ni element to flow from the MIG pool region to the plasma pool region. As a result, the Ni content is inhomogeneous in the hybrid pool, and higher in the bottom of the MIG pool region.(c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

A paraxial hybrid plasma-MIG welding process has been developed for joining middle-thick high strength steel plates. The study investigates the characteristics of the arc and metal vapor using an advanced three-dimensional spectroscope measurement system. The dynamic behaviors of the keyhole and element mixing are studied using a three-dimensional numerical model. The experimental and numerical results reveal that the Fe vapor ejected from the wire surface, along with the butting gap, significantly influence the arc characteristics, keyhole stability, molten metal flow, and element mixing.