Reduction of Oxide Inclusions During the High‐Frequency Welding of Steel via a Nonthermal Ar/H ₂ Plasma Jet

High‐frequency (HF) welding is an industrial process for producing longitudinally welded steel tubes, but its performance is limited by oxide‐related defects in the weld zone, which compromise seam quality. In this study, a nonthermal dielectric barrier discharge (DBD) plasma jet operating in an Ar/H ₂ atmosphere is, for the first time, integrated into an HF welding process for steel strip joining. The objective is to provide localized shielding and in‐situ oxide reduction during heating, melting and pressing. Welding is performed under identical parameters, with one region of the joint exposed to the plasma jet and another welded under ambient air for direct comparison. High‐speed imaging reveals more pronounced melting at the plasma jet interaction site, suggesting modifications of surface properties. Microstructural analysis by optical microscopy and FE‐SEM/EDS confirms a significant reduction of oxide inclusions in the plasma‐treated weld zone: Inclusions are fewer, smaller (≤4 µm) and mainly confined to the bottom region of the weld zone. In contrast, untreated regions contain larger inclusions, up to 27 µm, distributed across the weld zone. These findings demonstrate that a DBD plasma jet can be integrated into HF welding, offering a promising approach to reduce oxide‐related defects without complex enclosures or thermal plasma systems.