A fixture design for controlling impact of the airflow on laser welding of galvanized steels

Abstract

This paper examines the effects of horizontal airflow on laser welding of galvanized steels. A uniform laminar flow was delivered using a specially designed external airflow device, and its impact on vapor plume dynamics and keyhole behavior was analyzed with synchronized high-speed cameras. The analysis showed that, under Follow airflow conditions, penetration depth was notably reduced compared to Against conditions, with increased surface defects observed in galvanized steel. Keyhole instability, as observed in the frequency spectrum (≤500 Hz), was more pronounced under Follow conditions. Theoretical analysis identified two main effects: 1) Airflow in the Against condition helps maintain keyhole opening by dragging melt away, while in the Follow condition, it drags melt toward the keyhole, leading to shrinkage. 2) Airflow affects the plasma plume, with Follow conditions increasing laser energy attenuation and resulting in shallow penetration. A hollow rectangular block fixture was designed to shield the molten pool and keyhole region from airflow effects. CFD modeling and experiments with a 5 mm block demonstrated reduced airflow impacts, improved process stability, and defect-free welds in both bare and galvanized steel.