Mechanism study of thermal fluid flow and weld root hump suppression in full penetration laser welding of Al alloy with alternating magnetic field support

In this work, the influence mechanism of alternating magnetic field on the thermal fluid flow and weld root hump suppression in full penetration laser welding of aluminum alloy was studied. A novel three dimensional transient numerical model was developed, in which a multiple reflection laser beam model, a varied metallic vapor force model and an electromagnetic model including Lorentz force and Joule heat were considered. The experimental results indicated that when the effective magnetic flux density was 57 mT and its alternating frequency was 400 Hz, a sound weld bead for 10 mm plate could be obtained. The numerical analysis showed that the periodically varied electromagnetic force exerted an upward support to the weld pool, making its geometry and flow pattern stable. The keyhole collapse at upper and middle region was enhanced and the higher laser absorption was attributed to the decreased occurrence frequency of through-keyhole. The weld root sagging formation was instantaneous, while its suppression was a persistent process. The effect of weld root hump suppression depended on the dynamic competition among the electromagnetic force and the forces that promote the weld root sagging generation in the welding process. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

This study investigated the influence of alternating magnetic field on thermal fluid flow and weld root hump suppression in full penetration laser welding of aluminum alloy. Experimental and numerical analysis revealed that appropriate magnetic field parameters can effectively suppress the weld root hump and improve welding quality.